total is $800.19 without shipping and taxes or whatever but that looks good to me, the only thing is the graphics card; I don't know if you like ATI or NVIDIA. I thought the ATI one was a good value but I'm not an expert on graphics cards so maybe someone else can suggest something better.
Hope that helps,
EDIT: there's no keyboard/mouse in that one but you could pick that up for pretty cheap or just use the ones you have now.
Desktop: Dell Dimension E510, 2.5GB RAM, Intel P4 3.0GHZ, 250GB HDD, Windows Vista Premium. Might not be the best, but the old girl is still running good.