I have spent a while purchasing ex-Government PCs and LCD screens.
These PCs are a range of specifications although all are quite similar in speed. I have refurbished them all, installed hard drives and RAM, cleaned them up and installed XP on all of them. Each one has a valid XP Serial Number.
The range of specifications are :
Pentium 4, 2.8GHz -> 3.0GHz
40GB Hard Drive (can possibly be bigger)
512MB of RAM (be possibly be more)
15" LCD screen (the flat kind, not the old style)
Front and back USB ports
Speakers in the case (but you can plug in speakers)
Onboard sound/video/LAN
Machines are either IBM ThinkCenters or HP Compaq EVOs. An example of what they look like are below.
Machines are all built up ready to go. Mouse and Keyboard included.
Excellent for home as a PC for using the Internet, study/school etc. Could also play some basic games easily.
Depending on how far away you are, I'll also deliver it for you.
2.8 MHz System price is $200
3.0 MHz System price is $220
(Depends on what is available at the time)
Extras
Need a burner? I will install a DVD Burner for you for $40 extra.
Anti-virus? I use Kaspersky Anti-virus, which I can install for you for $35 (includes 1 year license)
IBM ThinkCenter :

HP Compaq EVO :

Pictures are purely for illustration purposes only.
If you are interested, drop me a line on here.
Cheers,
D