If you want to go the easy way out and skip all or some of the building, you can buy a "bare bones" kit.
A few weeks ago someone gave me $500 to build them a computer (this person very ignorant about computers and imply said "I just want a good computer so I can use the internet and use Word, Excel and check emails"). I didn't want to spend hella time on it so I bought a bare bones kit that included motherboard with integrated video/audio/network card, cpu, case, memory, 40gig harddriver, and CDRW for $159 total. The only thing I had to do was install the operating system and drivers, everything else was already assembled. easy money and I only spent a couple hours on it.