It is perhaps impossible to list out all possible problems that can be faced in Windows XP. So you are welcome to report problems at my forum.
Here are some problems that are encountered by the most of the people.
Whenever it is suspected that something wrong is started to run behind, disconnect your internet connection. It is the best practice to have any anti-virus installed in the computer whether offline or online and beside those there should be anti-spyware and other malware removing tools. Prevention Tools are discussed in my Recomended Software section. Do not trust any unknown sites if those claim that those can remove virus or spyware from your computer.
As a problem of sudden not opening task manager(taskmgr.exe), msconfig or regedit, you can take it almost for sure that there is some trojan horse running in background. So the attempts will be like these
Other known issues with quite the same solutions(except line no.6) are
Internet Explorer shutting down while trying to open,slow internet speed(depends on the symptoms whether affected by parasites), search engine changes, unknown sites and pop-up appears etc.
Most of these are due to the reason that some adware or spyware or other kind of parasites running.
For best practice never go online without strong firewalls installed and never browse through the sites that are questionable and if you do so do that at your own risk but try to be smart to disable active x controls,javascripts and other risky mobile codes. Lock your host file and never trust any unknown software to be downloaded.
I am not discussing elaborately at this time, go here.
First go to your device manager and see the error codes. Try to uninstall those in safe mode and open windows normally so that windows can redetect those at start up. But if that does not work and if that is CD/DVD damaged by any misuse of cd/dvd recording,formatting or other softwares you can follow microsoft's sugestion( http://support.microsoft.com/default.aspx?scid=kb;en-us;320553) or select your problem from this list.
To obtain or back up your drivers go to http://www.driverguide.com/
Check to see whether your auto play service setting is disabled. Go to Control Panel/Administrative Tools/Services/Shell Hardware Detection/
Open its properties by double-clicking and return this service to "Automatic" from 'Startup Type' drop-down menu. If that is already selected you may try to go here to repair registry for auto playing(line no. 234) here http://www.kellys-korner-xp.com/xp_tweaks.htm
This is a big issue, try reading these:-
This issue can occur if one or more of the PCHealth components in your computer are damaged. To resolve this issue:
1. It is important to note if you have recently made alterations to your computer before this problem occurred, or if the Help and Support
Center ever worked correctly. If you have recently made alterations to your computer before this problem occurred, try to undo the changes
you made or uninstall the hardware or software that could have caused the issue. After you do so, test to determine if the issue is resolved,
and if it is, skip the remaining steps. If the issue is not resolved, continue to the next step.
2. Remove the .cab files from the Packagestore folder, and then rebuild the original Help and Support Center:
a. Click Start, click Run, type "cmd" (without the quotation marks), and then click OK to open a command prompt.
Type "net stop helpsvc" (without the quotation marks), and then press ENTER.
b. Type "cd /d windir\pchealth\helpctr" (without the quotation marks), where windir is the Windows folder, and then press ENTER.
c. Type "rd packagestore /s /q" (without the quotation marks), and then press ENTER.
d. Type "cd binaries" (without the quotation marks), and then press ENTER.
e. Type "start /w helpsvc /svchost netsvcs /regserver /install" (without the quotation marks), and then press ENTER.
f. If any of the following processes are running, stop them: helpsvc.exe helphost.exe helpctr.exe
To stop a process, right-click the taskbar, and then click Task Manager. Click the Processes tab, click the process you want to stop,
and then click End Process.
g. At the command prompt, type "net start helpsvc" (without the quotation marks), and then press ENTER.
3. If the Help and Support Center has not been customized by an OEM, skip to the next step. If the Help and Support Center has been
customized by an OEM, completely refresh the Help and Support Center:
a. Click Start, click Run, type "cmd" (without the quotation marks),
and then click OK to open a command prompt. Type "net stop helpsvc" (without the quotation marks), and then press ENTER.
b. Type "cd /d windir\pchealth\helpctr" (without the quotation marks), where windir is the Windows folder, and then press ENTER.
c. Type "rd packagestore /s /q" (without the quotation marks), and then press ENTER.
d. Type "rd installedskus /s /q" (without the quotation marks), and then press ENTER.
e. Type "cd binaries" (without the quotation marks), and then press ENTER.
f. Type "start /w helpsvc /svchost netsvcs /regserver /install" (without the quotation marks), and then press ENTER.
g. Type "start /w helpsvc /register" (without the quotation marks), and then press ENTER.
h. If any of the following processes are running, stop them: helpsvc.exe helphost.exe helpctr.exe
To stop a process, right-click the taskbar, and then click Task Manager. Click the Processes tab, click the process you want to stop, and then click End Process.
i. At the command prompt, type "net start helpsvc" (without the quotation marks), and then press ENTER. NOTE: The preceding procedure should not negatively affect an OEM-customized Help and Support Center.
However, it does remove any other .cab files from the Packstorage folder, such as the Windows XP support tools (which adds their table of contents into the Help and Support Center).
4. If the preceding steps do not resolve the issue, use the Windows XP CD-ROM to start your computer, and then run a repair (in-place upgrade) installation.
Steven Liu
This edit resets the proper keys to invoke Help and Support, depending on your issues. Click here.
This script repairs Windows Help and Support if you have run any Reg Cleaners:
Repairs Windows® XP Help and Support after running Easy Cleaner or similar registry cleaners.
Note: If you have used Easy Cleaner, there is a workaround that prevents Help and Support from becoming corrupt: In the options, add Help to the Skip List.
http://personal.inet.fi/business/toniarts
Start Menu/Help and Support doesn't work: Go to Start/Run and type in: helpctr -regserver and Start/Run/CMD: regsvr32 /u hhctrl.ocx.
To reinstall Help and Support: Go to C:\Windows\inf\pchealth.inf. Right click and choose install. Have your CD handy.
Note: The folder is hidden by default. Go to Start/Run and type in: control folders. View: Show hidden files and folders and uncheck Hide extensions for known file types.
"Could not start the Help and Support Service on Local Computer. Error 126: The specified module could not be found" Restore Help and Support Service. Restore Help and Support Service Keys.
You may also opt to running the System File Checker. To do so, go to Start/Run/CMD and type in: SFC /Scannow. This option forces Windows to scan all protected system files immediately.
Restore winhlp32.exe for XP or XPSP1 (Line 57)
http://www.kellys-korner-xp.com/xp_tweaks.htm
After installing SP1 for some users the correct version of win32hlp.exe is not properly placed in the System32 folder. If this is the case replace the older version with the version found in windows\ServicePackFiles\i386.
Another option to the above:
1. Insert the Windows XP installation CD into your CD-ROM.
2. Browse to your CD-ROM and change the folder to \I386
3. Copy the following files into a temporary folder on your hard disk:
Winhlp32.cn_
Winhlp32.ex_
Winhlp32.hl_
4. Click Start->Run, type CMD and then press Enter.
5. Change to the temporary folder where you stored the Winhlp32 files.
6. Type the following commands:
EXPAND WINHLP32.CN_ WINHLP32.CNT
EXPAND WINHLP32.EX_ WINHLP32.EXE
EXPAND WINHLP32.HL_ WINHLP32.HLP
7. Copy Winhlp32.exe to your \%SYSTEMROOT%\ folder.
8. Copy the Winhlp32.cnt, and Winhlp32.hlp to the \%SYSTEMROOT%\Help\folder.
9. Typically this folder is C:\Windows.
10. Delete the contents of your temporary folder.
Checkpoint: Help and Support Won't Expand
Go to Start/Run/Regedit and navigate to this key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment. In the right pane, verify that the windir value is REG_EXPAND_SZ and not a REG_SZ type. If not, change it.
Tip: If you want to view only the locally stored Windows XP Help documentation in the Classic View: Go to Start/Run and type in: hh windows.chm
Check the default values for these registry keys to make sure that they match. Registry keys and values to fix XP's Help and Support after running Toni Arts EasyCleaner.
HKEY_LOCAL_MACHINE\Software\CLASSES\TypeLib\{FC7D9E00-3F9E-11D3-93C0-00C04F72DAF7}\1.0\0\win32
Default value: C:\WINDOWS\PCHealth\HelpCtr\Binaries\HelpCtr.exe\1
HKEY_LOCAL_MACHINE\Software\CLASSES\TypeLib\{FC7D9E00-3F9E-11D3-93C0-00C04F72DAF7}\1.0\HELPDIR
Default value: C:\WINDOWS\PCHealth\HelpCtr\Binaries\HelpCtr.exe\
HKEY_LOCAL_MACHINE\Software\CLASSES\TypeLib\{FC7D9000-3F9E-11D3-93C0-00C04F72DAF7}\1.0\0\win32
Default Value: C:\WINDOWS\PCHealth\HelpCtr\Binaries\HelpCtr.exe\2
HKEY_LOCAL_MACHINE\Software\CLASSES\TypeLib\{FC7D9000-3F9E-11D3-93C0-00C04F72DAF7}\1.0\HELPDIR
Default value: C:\WINDOWS\PCHealth\HelpCtr\Binaries\HelpCtr.exe\
Help and Support - Did you know not working...
Delete the following file. C:\WINDOWS\PCHEALTH\HELPCTR\Config\News\newsver.xml
Help and Support - Start Menu Doesn't Work
Go to Start/Run and type in: helpctr -regserver
Help and Support - Text is missing
Some themes can knock out the text in help and switching to another custom theme may not correct it. Switching back to an original XP theme - so far - will set things right again.
Windows XP Security Patch: Flaw in Windows XP Help and Support Center Could Enable File Deletion
http://www.microsoft.com/Downloads/Release.asp?ReleaseID=43681
The above patch resolves the "Flaw in Windows XP Help and Support Center Could Enable File Deletion" vulnerability in Windows XP. Download now to prevent an attacker from deleting files on another user’s computer, via either a Web site or an e-mail.
Restore winhlp32.exe for XP or XPSP1 (Line 57)
http://www.kellys-korner-xp.com/xp_tweaks.htm
More information on troubleshooting Help and Support, customizing and other extra issues can be found here:
Troubleshooting Help and Support
http://www.kellys-korner-xp.com/xp_h.htm#h&s
Help, CHM, HH Checker/Fixer (Line 141)
http://www.kellys-korner-xp.com/xp_tweaks.htm
Helpctr.exe not responding - Go to Start/Run and type in: Helpctr.exe.
For some users this has restored the functionality in the Start Menu.
Go to Start/Run and type in: helpctr -regserver
If the above didn't help:
Check your settings here: Go to Start/Run/Regedit and navigate to this key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session
Manager\Environment
In the right pane if windir is listed under type as REG_SZ, it needs
to be changed to REG_EXPAND_SZ, Value Data: C\Windows.
If this is the case:
Go to: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment
Right click on Environment, then choose Export, name it and save it. Then go to the right pane, right click in an empty area and choose New/Expandable String Value. Name it windir. Then double click it and under Value data, type in: C:\WINDOWS
From there, right click and delete the windir which type was listed as REG_SZ then hit refresh (F5).
Have you disabled it by mistake? Open your system in safe mode and try to enable or uninstall your password.You can download this program to reset/re-enable your administrator account. You can enable administrator account at logon screen by running this program.
Computer Restart or Shutdown Problem
Windows XP logon screen does not appear and the computer continuously restarts
http://support.microsoft.com/default.aspx?scid=kb;en-us;310396
You cannot log off, restart, or shut down your Windows XP-based computer
http://support.microsoft.com/default.aspx?scid=kb;en-us;831431
After you install Windows XP Service Pack 2 or Windows XP Tablet PC Edition 2005, your computer restarts continuously
http://support.microsoft.com/default.aspx?scid=kb;en-us;873161
Black startup screen is briefly displayed and your computer restarts repeatedly when you try to start Windows XP
http://support.microsoft.com/default.aspx?scid=kb;en-us;314466