unfortunately there is no common fix for this issue...some times it's malware related and sometimes not....i'm gonna make two suggestions here...one for those with the xp cd..and one for those who don't have it....the first suggestion is a repair install of xp...this will not cause you to lose your data...but you will have to re-download all of the windows updates...the other is a trip through the malware forum (this one you all should do justs to be safe...and probably should be done before the repair install if possible)
Boot up with the XP CD in the drive and let Setup run. Go past the "C" and "R" repair options by presssing Enter just as if you're doing a clean install and you'll eventually get an option to "Repair an existing installation". That's the one you want. If it asks about formatting you've gone wrong, so start over.
You'll get to keep your existing apps & settings, but you need to re-install SP2, Windows Updates & any unsigned drivers afterwards. NOTE: Be aware that you'll lose any protection from Blaster / Sasser type worms. Don't go online without a firewall, whether the built in Windows one or 3rd party.How to Perform A Re-Install Of XPRepair XP
Please go to the malware
forum in my signature and follow the instructions at the top....Especially the CLICK HERE
That will give you several steps that will help you clean up 70 percent of all problems by yourself. If at the end of the process you are still having difficulty--and you may not be-- then post a hijackthis log in THAT
If you are still having problems after getting a clean bill of health from the malware expert, please return to this