[ViN86]

You should really check out the new AMD Fusion APU's. They are cheap, powerful, and low power. Also, they have a pretty powerful on-die GPU that can actually play games. Also, if he's really into programming, the chip offers a good opportunity to get into OpenCL. Let's price one out:

AMD A8-3850 Llano 2.9GHz 4MB L2 Cache Socket FM1 100W Quad-Core Desktop APU - $140
GIGABYTE GA-A75M-UD2H FM1 AMD A75 (Hudson D3) HDMI SATA 6Gb/s USB 3.0 Micro ATX AMD Motherboard - $100
CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory - $60
Thermaltake VL84301W2Z V3 Black Edition with 430W Power Supply ATX Mid Tower Computer Case - $70
Western Digital Caviar Black WD5002AALX 500GB 7200 RPM 32MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive - $60
Acer G245HBbd Black 24" 5ms Full HD WideScreen LCD Monitor - $160

Total Cost: $590

That's with 8GB RAM and a 24" LCD heh.

EDIT: Forgot a hard drive, added