|Ideas are run sfc.exe /scannow. Needs xp disk.|
Run repair from xp disk if you have a xp disk.
Might be possible to run a system restore point.
Might have to move off important data and then consider restore to oem state. See manual, you might have disks or might have to make them or use a boot F key to access repair features.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10