I've just built a whole bunch of PC's most using vista but one i've installed XP SP3 so it can run specific software
Twice i've done clean XP installs and within a week the registry gets corrupted with a message saying that there was a registry issue and XP has fixed it from a backup.
I've run memory and HDD tests and I doubt reformatting and doing another clean install will help unless I can trace the problem. It's got power to burn, E8400 w/ 2G RAM.
All it has is XP SP3 installed then full updates run including IE7 and .NET 2 + 3.5.
Could be MS updates, the first install started failing after upgrading to IE7 which was a day after installation, 2nd install didn't start failing until after Office was installed several days after I set it up.