Repairing computer from SP3 to SP2

I recently installed SP3 and it caused my pc to the never ending boot cycle. So I was searching about it and input the error in another computer on google "you computer did not find this file, so either use BART-PE or your Windows Disc to repair". I put in the Windows disc and it worked. I registered the product key again and when it booted then all the files were back. My question is that windows keeps telling me to install all these updates, naturally I just say ok to it and then fails and tells me to install again? Does anyone know whats going on? Thanks.

It seems to me that the SP3 update was not successful and you mentioned that your Windows disc repaired the system. Have you got SP2 installed prior to updating to SP3? Were your windows disc was containing the SP2 update? What is the current version of the OS? Check from start > run and then enter winver and then click ok.

Thanks for replying, I was having SP2 installed previously. The disc is for SP2and the version number is 5.1.

I think that you might have a composite of SP2 and SP3 files on your system, since SP3 never installed or was removed correctly. To add to this mess, if you had IE7 installed when you repaired, using the WinXP SP2 disc, this too could be adding to your issues. So follow the below links to solve your problem:

How to perform an in-place upgrade (reinstallation) of Windows XP
http://support.microsoft.com/kb/315341

Release notes for Windows XP Service Pack 3
http://support.microsoft.com/kb/936929

The hard disk space requirements for Windows XP Service Pack 3
http://support.microsoft.com/kb/947311

Steps to take before you install Windows XP Service Pack 3
http://support.microsoft.com/kb/950717

Some third-party programs may experience a change in functionality after you install Windows XP Service Pack 3
http://support.microsoft.com/kb/947309