What happens when you run a compatible combination, like PR7 + XP 32, or CS4 + Win7 64?
I'm sorry but I have no idea what you are asking me. I thoroughly explained what is happening. I explained that when I run Premier/Media Encoder under XP SP3 it's all good and that when I run teh same under Windows 7 64 bit it's not. What is PR7? The version of Premier in CS4 (updated) is 4.2.1 (on both machines). Media Encoder is version 4.2.0.006 (on both machines). What do you mean by a compatible combination? I'd expect a fully updated CS4 to be completely compatible with Windows 7 64bit. I don't remember there being a 32 bit and a separate 64 bit CS4 offering. In fact I just talked to Adobe support and tehy confirmed this. Same package for both 32 and 64.
I misread the big 7 as meaning PR7. Sorry to mislead you and to have misread your post.
It could be a myriad of things, but look at the second link in this link: Some suggestions...
There is some info requested, like Process Explorer (not Task Manager) and DXDIAG. Maybe that will shed some light, but temps and voltages are the first suspects.