Windows 7: System restarting all of a sudden

Hey guys, i've been having this problem for a while; sometimes the computer just restarts instantaneusly and it always does this right before something memory consuming is about to happen (ex. a game loads, windows loads etc).
My guess is the memory is causing this, or the lack of it, but i have a friend with almost the same computer and with Windows 7 and he never got that restarting.
Also here are my specifications

intel core 2 quad 2.4 ghz
2 gb ram
windows 7 64bit
nvidia 9600 gso 768 mb/ram



Ow, and the only difference with him is that he has Windows 7 32bit.

Hi,

* In this regard, I would suggest you to increase the page file size

You mean the virtual memory?

Yes, That's right

Ok, i increased the paging size, don't know if that helped or not cuz those crashes were completly random but, it is true that the recomended virtual memory was 3 gb and my virtual memory was 2 gb (now it's 5 gb) so that might just be the solution.
Thnx for the help .

Glad to hear that my instructions have helped you. However, keep me posted if the issue was completely resolved. If not, we can try alternative solutions

Ok, i just had another random restart . So i'm guessing it's not from the paging size, what do you think it could be?

* At this point, the issue might be with the heat sync. You could have a check of it

* Or, you may have to notice carefully if this occurs when you open a specific application

Well, i don't know how to check the heat sync but i'm pretty sure it doesn't do that for a specific application or type of application, well, it does: only for games but regarding the games it does it for any game i mean i had this happening for company of heroes, test drive unlimited, wow and trackmania nations, so i don't really know what the algorythm would be :-/ .

[Edit]

Ok, it doesn't do that for only games, for example, 5 minutes before i edited this message i just had a sudden restart and at the time i was talkin' to my friend on xfire (with the mic), listening to music on winamp and working on a model in mudbox :-/ .

Just my 2-cents but wouldn't it be better on x64 if you were 4 gigs or more and then let the os manage your page file?