I've recently encountered a problem in which my computer is in a continuous logon logoff loop and I can not access my windows username. Safe mode fails, even under administrator. I researched online and discovered that the issue is likely the result of Ad-Aware removing/destroying a neccesary registry key. I followed the guidelines as stated at Quick Launch settings are not saved; Search Assistant Toolbar in Taskbar (From "Here is the solution to the logon - logoff issue in Windows XP") on, but no luck. Typing COPY USERINIT.EXE WSAUPDATER.EXE fails, and the computer tells me it in an invalid command. I'm stumped and hoping someone can help me fix the issue without resorting to a reformat. Or if I can reinstall Windows without destroying any of the personal files on the computer.

Were you referring to this:

http://thinkinginpixels.com/quick-fi...nlog-off-loop/

Otherwise a Repair Install should retain your programs and data.

You will just need to reload any service packs beyond what is on the CD.

This is assuming you have a retail version of XP.

If you have a manufactured computer the manufacturer might have a different approach to the Repair Install.

Repair Install XP
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1) Boot with the Windows XP CD and at the Setup Screen press the Enter key

2) You will be taken to the Windows XP Licensing Agreement. After reading the agreement press F8 to proceed

3) The next screen gives you the option to do a fresh (clean) install or to "Repair the selected Windows XP installation." Press "R".

4) Windows XP will copy the necessary files to your Hard Drive to begin the installation and will then reboot. You will see the message that informs you to "Press any key to boot the CD". Do Not press any keys this time just wait a few seconds and the Windows Startup Screen will be displayed. Following this you will be greeted by the Windows XP Setup Screens.

5) When Setup has completed you should find all of your previously installed applications and settings are intact.