Points will be awarded for possible sources of the problem, since the computer is in the shop (and will hopefully be fixed w/o wiping my drives).
Comp configuration is a dual boot. 2 physical hard drives: WD200JD SATA drives (Identical). I installed XP 2 on the first hard drive after partitioning C: as the windows/programs drive and D: as data. I then installed kubuntu hoary on the 2nd hard drive w/ the linux partitions and a G: to be shared between OS's. Grub boot loader. System was working dreamy for 3 weeks until yesterday. . .
I left the computer on over night to complete a download in XP and awoke to a black screen stating kernel panic. Apparently the system had magically restarted overnight and failed when booting to the default OS: linux. I restarted the system and the usual grub menu came up, so I chose XP. The screen went blank - completely black and didn't move. On the next restart, I tried linux again to find the kernel panic error. Ran memtest86 w/ no errors. Tried booting again, w/ no success. I tried to run the WD drive diagnosis utility and started w/ a quick test (supposed to take 5 mins). 10 mins later I came back to find the test had progressed very little and was frozen. I tried to abort the test, but since it was frozen, had to hard reset it. Any attempts to run the diagnosis tool following would end up freezing prior to the menu. I had an extra 2 dimms lying around so I switched the memory and reran memtest86 w/ no errors. I updated to the latest bios and no change.
Now I'm thinking it is a motherboard problem or cpu vs. a hard drive problem. Why? Because the OS's are installed on different physical drives and neither of them can boot. I would appreciate any thoughts and suggestions. . . Since the comp is already in the shop, what would you have done if in my shoes?