vista crashing on idle

[r_j_k_p]

i have windows vista home premium 64 bit.
i havent made any hardware changes recently, but when i leave my pc on for an hour, and then return to it, i find it crashes.
like it comes up with that cirle icon meaning that it is doing something, but then the whole screen goes a whitey colour, indicating that explorer.exe or something has crashed.

has anyone had anything like this and if so what solutions can you guys offer?

many thanks!!!

[Blitzen]

Sure its not in hibernation?

[r_j_k_p]

how do i check?
but ye pretty sure
i just leave it on desktop and when returning hours later, the things i said happened

[pp05]

I have a similar problem in XP. I will switch screen names and leave pc running with welcome screen showing. When i return it takes ages to load up. Is very slow and I'm also hoping someone might have some tips. My hard disk only has 4gig spare.. will that have anything to do with it?

I think for vista there is a patch for it or there was one announced - maybe sp1 will have it.