Multiple HDD XP installaion question

I am in the process of upgrading my compter and I can't remember how to configure my hard drives for the best performance. Here are the essential specs.

Old Comp
amd xp 2000+
ECS crap mb (k7s5a pro)
512 (256x2) ddr 266
ati 9600 pro
various old pata hdds (10gb, 13gb, etc)
80gb pata 133 -> current primary drive to be moved to new comp

New Comp
intel pent d 820 (to be upgraded to core 2 duo later)
Abit IB9 p965 MB (its new, but it looks good so far)
1 gb (512x2) ddr2 667 (to be upgraded to 2gb later)
xfx 7600gt
Seagate 160gb sataII -> to be the new primary drive

I use this comp for internet, some audio editing, some CAD, some gaming - C&C mostly and I would like to play C&C 3 when it comes out in march.

How should I partition my drives and where should I install xp, my programs, and my data for the best perfomance?
Thanks.