Rebuilding PC

[donsor]

Following a disaster of my PC, I've decided to do major invasive surgery. I've done a couple of rebuilds before but I've forgotten some of the critical procedures and I need help.
PLAN
1. Replace the mobo with an Asus M3A32-MVP DeLuxe Wifi .
2. Install an AMD Phenom 9500 Agena AM2 Quad Core
3. Install a new 400G Seagate Barracuda 32M Buffer
3. Go with Vista 32bit Home Edition

I'll keep the Antec Sonata II case with 430W PSU.
I'll keep the EVGA GeForce 7950GT video card until I can afford to upgrade with 8800GT.
I'll keep the SB Audigy 4 sound card

QUESTION
1. What can do with the two existing (74G Raptor & 300G Maxtor SATA) drives. The Raptor has the WINxp Home Edition SP2 OS.
2. Do I have to buy a new OS or can I use the existing WinXP?
3. If I go with Vista I've read that I have to have the necessary drivers ready. Did they mean drivers for the video and sound?

Any input will be highly appreciated.