Random crashes.

[HackSore]

I have been experiencing some seemingly random crashes lately, and one i had the other day seemed to tie in with "An error was detected on device \Device\Harddisk5\D during a paging operation." in the event viewer.
Now on checking the viewer, it seems recently this specific warning has cropped up a lot, over 3 different disks, being harddisk 2, 4 and 5.
I have 4 disks in my machine, one of them partitioned into 2 drives.
After a bit of googling it seems that a few people encountering this error message after testing found it to be faulty RAM.
I have just run diagnostics on the motherboard and CPU, and some tests on the RAM (although not extensive) and they have all come back fine.
I will run extensive ram tests tonight to see if it picks up anything.

I am praying that it isnt a hard disk problem, as i have a hell of a lot of music and stuff i have written and recorded over the years on them, and cant really afford to lose any of it.
Can anyone recommend a hard drive test that will be safe to run? (im so paranoid about my drives!)

Or any ideas about what else could be causing the problem?

Thanks in advance!

[HackSore]

Hmm, after another crash, it would appear that the error doesnt coincide with the crash, but when windows is starting up. Strange.
But the crash only seems to be happening when im playing fallout 3, which is a bit of a relief, as its unlikely to be a hard drive issue.
Gonna try some general cleanup and defragging on the windows drive and try updating drivers and such for the crash problem.