Second Sata stops being recognized!!!!

I have 2 Seagate Sata Drives The first Win XP pro is booted on, the other is just for storage- it is also about a year newer.

When I turn my computer on, the bios recognizes both hard drives. What I have found is that now, after windows and associated programs have completely loaded, the hard drive will dissapear if not used. If I run a video or some other application it will prolong the Hard drive's dissapearance. Any ideas? The stata cables are fine, and I havn't yet checked the hard drive in another computer to see if it is that or my mobo. But do you think it could be a virus or a hack? Anyone The hard drive doesn't have any bad sectors on it when i ran a scan disk the integrity of the drive is fine, it seems like it is some other component on either the hard drive or the mobo, but I can't tell. know what kind of problem this could be?