Try this:
Budget $500 home computer
The last list of specs on there, only replace the case with an Antec Three Hundred (the one listed is kind of shoddy). Should be a very good, quality mid-range computer and with the Antec case comes to about $515. I was going to make it for my dad for father's day, but I checked with him before I started and he flatly refused it, said he was happy with his old P4 machine. In any case, the one I specced by the end is a pretty solid build that will do internet, video, light gaming, just about anything a normal user would do and I recommend it.