So i've been working on a clients computer. they are having random restarts. it doesn't seem to have any particular time or event when it occurs. i have checked event viewer, as well as ran extensive, memory and CPU tests. i have swapped out the PSU for a known good one to no avail. the computer will not shut down if you are running a test off a bootable cd or if in bios, but will shut down if in windows? could this be the hard drive itself? any help would be appreciated. this is running windows XP Pro. pentium 4 system, 256 mb ram, pretty basic system. Thanks.