Yes, that did help; however, I actually went through a very similar scenario.
My sys:
Phenom II x4 955black
4G Ram
Radeon HD4870
Windows 7 64Bit Ultimate
Antec Nine-Like Case
Corsair 850W PSU
Causes of startup crashes:
1. USB Attached External 1TB Drive (simply unplug till windows starts)
2. PSU -- if your PSU is under 700W and you have 4 or 5 devices hooked up to your PC -- this is it.
(Buy a bigger PSU pref. Corsair)
Causes of GPU crashes (3D Game crash after a few mins):
1. Heat : If you got a smaller case and you're not cooling your system with case fans or heat-sinks, etc. Heat is your problem. If your PC is next to a heat radiator; heat is probably an issue. If your vents are clogged to the core with dust, heat maybe an issue. If you got cheap buying a good PSU, guess what? Heat maybe your issue. I've listed the problems that I ran into building my first system; so, don't feel too bad.
2. GPU Fan speed. Basically if it spins too low due to either a power deficeincy or bad drivers, your system heats up and/or crashes (or windows crashes it) to prevent pottentially worse problems. Most people who have similar setups have said that manually manipulating their GPU fans via 3rd party software did the trick. Before retorting to hardware solutions, this seemed to work for me as good remedy.
3. Sound Cards -- disable your sound card until you find drivers that work. Use whatever standard driver that Windows initially allocated. I realize you miss out on the 7.1Channell 3D sound; but, it's better than system crashes, I suppose, until some good drivers come out at least.
4. Window 7 64bit. I've had both. The 32 bit is more stable.
5. Pinnacle Game Profiler -- though seemless with 32 bit; it doesn't seem to work well with windows7 64bit.