Now that was important info left out.

( This may be video driver
related.
This generally has to do with display drivers. If you have recently done so
or ran the MS updates to do so, try a rollback via the Device Manager. If
this is not the case, use Ctrl/Alt/Delete and end process on Explorer.exe if
it is listed and either way, then go to File/New Task (Run) and type in:
Explorer.exe.
Explorer.exe repeatedly quits unexpectedly in Windows XP
http://support.microsoft.com/?kbid=883791
If still nothing:
Restore Taskbar and Desktop to Default Functionality (Line 164)
http://www.kellys-korner-xp.com/xp_tweaks.htm
To use the VBS Files: Download .vbs file and save it to your hard drive (you
may want to right click and use Save Target As). Double click the vbs
file. You will be prompted when the script is done.
NOTE: If your anti-virus software warns you of a "malicious" script, this
is normal if you have "Script Safe" or similar technology enabled. These
scripts are not malicious, but they do make changes to the System Registry.
Added info and help:
Taskbar Repair Tool Plus!
http://www.kellys-korner-xp.com/taskbarplus!.htm
Added info, not knowing more.....
Computer Stops Responding with a Black Screen When You Start Windows
http://support.microsoft.com/directory/article.asp?ID=KB;EN-US;q314503
Windows XP Stops Responding at the Welcome Screen
http://support.microsoft.com/support/kb/articles/q294/4/27.asp
And lastly:
How to uninstall SP2: Uninstall SP2
Start/Control Panel/Add or Remove (make sure that Show Updates is enabled).
How to do a repair install:
Repair the Windows XP Installation - Note: You will forfeit all MS Updates.
Configure your computer to start from the CD-ROM drive. For more information
about how to do this, please refer to your computer's documentation or
contact your computer manufacturer.
Insert your Windows XP compact disc (CD) into your CD-ROM drive or DVD-ROM
drive, and then restart your computer.
(You can also boot with a Windows 98/Me Startup disk with CD support and run
WINNT.EXE in the I386 folder on the CD)
When the "Press any key to boot from CD" message is displayed on your
screen, press a key to start your computer from the Windows XP CD.
When you see the following message displayed on the Welcome to Setup screen,
press ENTER: To setup Windows XP now, press ENTER.
At this point an option to press R to enter the Recovery Console is
displayed. Do not select this option.
On the Windows XP Licensing Agreement screen, press F8 to agree to the
license agreement. Make sure that your current installation of Windows XP is
selected in the box, and then press the R key to repair Windows XP. Follow
the instructions on the screen to complete Setup.
Perform an In-Place Upgrade (Reinstallation) of Windows XP
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q315341
--
In memory of our dear friend, MVP Alex Nichol
All the Best,
Kelly (MS-MVP)
Signature changed for a moment of silence.
Rest well Alex and we'll see you on the other side.
Troubleshooting Windows XP
http://www.kellys-korner-xp.com