"PC Load letter? What the F**K does that mean!?" lol....office space...great movie
So basically you need the case, RAM, processor, motherboard, HD, graphics card, keyboard, mouse and speakers and want to pay no more than $500?
Well depending on how good of a computer for him you want to build will determin what parts I'd suggest.
What kind of games does he play right now?
How powerful of a machine are you looking to get exactly?
If you can...go through his games collection and see which ones he has unless you know so I could get a general idea of what he plays.