Help!! Stop the Restarts!!

[This_Is_That_Guy]

Please someone Help!

I have a forum thread at;
http://www.linuxforums.org/forum/misc/166739-help-stop-restarts-new-post.html

But am posting here as I'm desperately looking for as much help on the matter as possible.
My original post;

I'm not entirely new to linux but still have alot to learn so please be patient with me if a say something stupid.

I'm having major probs I've been trying to get a multiboot set up going with different linux distros and Windows 7.

For some reason my computer is having random reboots. This happens with various distros so I don't think it specific to the distro. even booting to a live CD will do it sometimes. It doesn't appear to happen on Windows 7 though so I'm thinking it is one of three things;

1)Faulty Hardware, have tested the RAM & CPU etc and found no prob plus can run demanding games on Windows 7 perfectly fine so am less inclined to think that this is it.
2)Hardware incompatibility with Linux in general, not sure on this don't know a lot about it. Will list my hardware below.
3)Problems with ext4 fs, I'm thinking this is unlikely but with Win 7 and my Linux Distros being partition separately on the same HDD the only difference I see is the fs (NTFS & ext4).

I could be completely off on all of the above so if anyone can shed any light on to this please, help me. I really don't go back to just windows and let my windows only friends say I told you so...

My hardware:
Motherboard - Gigabyte GA-M55SLI-S4 F10
AMD Athlon
x2 64 Dual Core Processor
Nvidea GeForce 8600 GT
1x 320 GB SATA HDD

1x 500 GB SATA HDD
PATA DVD Reader/Writer

I am now just running Debain - Lenny.

[JJ 3000]

For some reason my computer is having random reboots. This happens with various distros so I don't think it specific to the distro. even booting to a live CD will do it sometimes. It doesn't appear to happen on Windows 7 though

Are you installing the linux distros on a separate hard drive?

When the restarts happen with the live cds are you accessing the hard drive(s)?

Do the restarts ever happen during installation?

What  is the wattage rating of your psu?