Picking the parts for your computer is one of the most important things in building a computer, because you cant assemble a computer without the parts! Picking parts for computers has become much easier than before, because things have been standardized, however, you need to make sure everything will fit. The first thing to think about when choosing the components for your computer is what you are going to be using it for. If you are creating a computer for just checking your eMail and using word, you are going to need much diffrent parts than a computer that you are going to be using for gaming.
CPU
The first thing you should pick out about your computer is what CPU you are going to use, because it determines what motherboard you are going to get, which determines what other components you get. There are two main CPU manufactruers, Intel and AMD. Both have their Pros and Cons, but they are pretty similar. I would suggest using AMD, because they give you a little more bang for the buck.
Here is a brief overview of the diffrent Intel and AMD CPUs:
Budget: AMD: Sempron
Intel: Celeron D
Midrange: AMD: Athlon 64
Intel: Pentium...