Windows XP constant Hard disk scans

Hey, one of my friends just asked me to help him find out why his computer always runs a disk check every time he boots up. I know this guy and he usually will not jus pull the plug out of his computer or something while its one, so his not imporperly shutting the computer down. I have no idea why its happening. Any sugesstions on how to fix it, or could it be a virus?

Thanks in advance.

Depending on the partition XP insists on running CHKDSK on, open Windows Explorer | Right click the partition in question, and select "Properties" | "Tools" button | Error-checking-->"Check Now" button | In the "Check Disk" window that opens, put a check next to "Automatically fix file system errors | Click the "Start" button | Do this for each partition CHKDSK runs on at boot. If the partition that CHKDSK runs on at boot is the root volume, then when you click the "Start" button to run a scan on the volume from within Explorer...you'll be asked whether or not you'd like to schedule the scan for the next reboot, in which case answer YES, then reboot.