Is this a decent computer build?

Since you didn't list a GPU, a sound card, raid controller or Blu-ray drive, it seems that you are sincere about it being a basic computing machine. In that case, I'm lost as to why you would want a 64-bit OS 4GB of RAM and a processor that is that fast. I'd also argue that a 550W power supply is overkill. for a machine that isn't going to be used for gaming, HD video, or serious photo manipulation, you're spending too much on parts that will never be fully utilized.