I have a 12 year old home built computer running winXP sp3 and a 1+0 Adaptec software RAID. Replaced Power supply with PC Cooling unit a couple of years ago. Have replaced several of the Seagate Cheetah drives as the machine runs 24x7. The other day the computer started up and shut down in 10-12 sec before I can enter the BIOS and without any beeps. I tok out and replaced the battery to reset the CMOS. I can't find any obvious shorts. I doubt the power supply has gone bad, but I do have a tester, just haven't done it yet. Other suggestions? Thanks.