|yeah not $400. i probably wouldn't spend more than $250 on a used system, because once you start hitting about $500, you could buy a NEW system with WAY more upgrade potential.|
the one you're looking at only has a single gig of RAM, but it's DDR1 (outdated hardware). you list the CPU as 3ghz, so i'm guessing this is probably a single-core Pentium 4 (also outdated hardware). A current Core 2 Duo would have comparable performance, multitask better, suck less power, and create less heat.
no mention of a graphics card either.
Free antivirus solutions are at least as good as the ones you'd buy from Norton/McAfee.
M$ Office is expensive, but OpenOffice (openoffice.org) is free and compatible with Microsoft Office.
in general, i'd almost always recommend against spending cash to buy a used PC from another person. The hardware technology just evolves too quickly, and the hardware itself degrades too quickly.