Newegg 'barebones' computers
Eg, "ASUS T3-P5G965 Intel Socket T(LGA775) Intel Core 2 Duo / Pentium D / Pentium 4 Intel G965 Barebone - Retail" - you can snag that for, as they say, about $200ish after shipping. The only downside is that the included power supply may be a bit 'deficient' if you want a high-end graphics card. See below for more notes.
Then you plop in a CPU, say a Pentium D 925
for $86 before shipping.
Then grab 1 gig of DDR2
for $100ish before shipping.
Et voila, new computer.
You can probably transition your old hardware over with some fiddling.
(keeping in mind the video would still be integrated and hasn't improved much over the 845. In addition selling the hardware you don't keep would net you some cash to cover part of your upgrade cost - a decent graphics card shouldn't be too expensive though.
Additionally, if you want to put this together entirely yourself, then you may be better off pricing out a decent case and an i965 board - for example the Rosewill or Cooler Master cases, and the MSI G965M-F LGA775 board)
Edited by - Hahukum Konn on 5/6/2007 10:22:48 PM