Windows 7 64 Bit. I was looking a bit and I think the problem is that if the CPU/GPU get at a certain temperature, it decreases the amount of work in order to help them cool down. However, for BTC Guild, it shows it as running but I'm not getting an shares. My mh/s is slow, but I should still be getting some shares.
If you are going to take a crack at mining you really should get and learn to use cgminer.