Freezes in games and generally all programs

I am soooo tired of trying to find the solution to the following problem:

WoW - wouldn't install and froze when it neared dowload completion. Ran as
admin which worked ok but then had to move the entire folder to the desktop
so that i could do the same thing for all the patches. took maaaaaany days.
Now it works great and smoothly for like 10 minutes before the whole thing
freezes.

Games in general - repeat the above. Although admittedly I only installed 1
more (a vista comp game).

Installing or downloading programs/patches/drives (even windows update) etc
in general - repeat the above.

Then at the end of the day when I think I finally have got things to work in
this heavy handed manner.... everything freezes anyways just a little later.

The computer is brand new (4 days old) and I have been struggling with it
ever since I got it. It is an HP something (bought as gaming pc via the
sellers), has nvidia drivers which I understand is a problem but I have the
latest drivers. Ehm, loads of RAM and duocore (and no big programs other
than wow... not even office or anything). Latest dirctx. Vista Home
Premium. It should work like a dream but its a complete fiasco. Don't even
know if this is a gaming problem or a general one or even if its vista or
nvidia... Does anyone have any idea? I really hope so (I can't bring myself
to try to figure this out googling any more.)

Clearly I am at my wits end...:-(