i would say power, heat, etc.
But there is also a matter of power management and drivers, especially video drivers. If the BIOS power management is set incorrectly, Standby can put your computer into a coma, screen saver could send brimstone of blue hell, and all of the TV specials would be cancled. Well...maybe not that far, but ti can be pretty bad. I would jump into to see if ACPI 2.0 is at least enbled, and all other power bios functions are "disabled" if they are by default.
PLEASE MAKE SURE ALL OF YOUR IDE DRIVE JUMPERS AND DRIVE POSITIONS ARE PLUG INTO THE CORRECT POSITION OR YOU WILL HAVE SYSTEM STABLITY PROBLEMS. The end of the cable is master only. So, don;t set the end of the IDE cable as slave with the jumper and hope for the best. Also, if you have a single drive on an IDE cable, make sure it is on the end connector and set for Cable select "CS".