First let me say thanks for providing this great resource.
I recently did my first build. I just read online how to do it, found corresponding parts and went for it.
I'm running a AMD Athlon II X4 630 Quad on a ECS A785GM-AD3(1.0) Motherboard, with a 600w PSU. My graphics card is a NVIDIA GeForce 7300 se.
So far there are no problems at all. In the beginning (eg. first day) I didn't have the heat sink on correctly. It kept coming unattached inside (unknown to me) and the computer kept shutting down. I figured it out and put it on and smooth sailing since (6 months).
But I'm worried it may be running hot. Nothing seems wrong, but I'm getting weird readings. Perhaps the heat sink or paste isn't working since it fell off a few times?
I have a 120mm intake fan on the side, a 80 mm exhaust fan on the back and the PSU has an exhaust fan.
Clean thoroughly all the dust inside the PC, video card included. What's the CPU voltage in the BIOS, you can manually set that to 1.2-1.25V if it's higher. Does your video card have a fan on it or it's with passive cooling, its temps are high. If it's with passive cooling a side case fan to blow on it would help but better get a new video card or take it out and use the onboard video on the motherboard.
Those are fine readings. The graphics card could definitely be lower, but it's not dangerous. The CPU temps are completely fine.
But wait-the GPU is at 90C on *idle*? That's very strange, and would suggest that either something's running it in the background or there's a bad airflow problem. Get some kind of program that can monitor GPU load, and see if it's working.
What are your load temperatures?