2x 512 meg Sticks of Twinmos, likely BH5 Ram
http://www.newegg.com/Product/Product.asp?Item=N82E16820218062R
71$ (Only refurb available at the time, but it's fine to buy)
DFI Lanparty Ultra-D Motherboard, you need a good mobo, and it supports PCI-E
http://www.newegg.com/Product/Product.asp?Item=N82E16813136152
135$
eVGA 6600GT PCI-E, you may opt for a 6800 as well, but PCI-E form is expensive for them
http://www.newegg.com/Product/Product.asp?Item=N82E16814130214
164$
Pioneer DVD burner, im not expert but this seems good
http://www.newegg.com/Product/Product.asp?Item=N82E16827129161
47$
AMD Athlon 64 3000+ Venice, comes with heatsink and fan, you can overclock this alot later
http://www.newegg.com/Product/Product.asp?Item=N82E16819103537
146$
Thermaltake TR2, their new 24 pin power supply, seems good so far
http://www.newegg.com/Product/Product.asp?Item=N82E16817153023
39$
This totals 603$, which leaves you enough for a keyboard, mouse and screen and maybee some non stock cooling.
If you get a PCI-E 6800 it's 663 with a 20 dollar mail in rebate total
http://www.newegg.com/Product/Product.asp?Item=N82E16814130231
EDIT: If you not comfortable with buying refurbished ram, we can throw in some better ram. I also left out a few dollars for a case, as you will want to probolly pick one up locally. Also the hard drive is not included with this, because you can probolly pick one up cheap from a best buy or ect, or have one.
Here are two fast WD hard drives for 56$ if you need as well
ATA
http://www.newegg.com/Product/Product.asp?Item=N82E16822144122
SATA
http://www.newegg.com/Product/Product.asp?Item=N82E16822135106
