If you want best performance and value for money, get socket 939:
CPU: A64 3000/3200+ (Winchester Core, 90nm)
Motherboard: Asus A8V Deluxe Rev2 or MSI K8N Neo2 Platinum
Then OC it...you know you want to...it's free performance... :bigsmile:
The memory and HDD you selected look good - i'd stick with them. As for the video card, a good choice would be an Nvidia 6600GT (AGP version).
One point though, you might want a power supply with more grunt, especially if you want to overclock eventually. Supplies made by Antec or Enermax are always good - such as the Antec 430W TruePower. Remember that the components can only be as good as the quality of the power supplied to them...so it's worth spending a little extra on a good supply.