MS considers a new mobo a new computer, not a hard drive (thankfully).
Newegg.com - G.SKILL 1GB (2 x 512MB) 184-Pin DDR SDRAM DDR 400 (PC 3200) Dual Channel Kit System Memory Model F1-3200PHU2-1GBNT - Desktop Memory
$32. Go for two if you can.
Newegg.com - G.SKILL 1GB (2 x 512MB) 184-Pin DDR SDRAM DDR 400 (PC 3200) Dual Channel Kit System Memory Model F1-3200PHU2-1GBNT - Desktop Memory
$32. Go for two if you can.