Sound Drivers - Just wait and they'll show up.. EventuallySmatteo,
Windows has a valid driver that works with it (i'm using it on my Vista partition). Simple way to get the device driver (and you can actually watch it perform the operation) is to open device manager (leave in separate window), and then go to the security center and let it do the "auto updates" for Vista. Within a few minutes of confirming your internet connection works, you'll see Vista begin downloading the new updates for your release canidate. It was around 45% on my system before the device manager screen started flashing like crazy. Within another minute, the "unknown multimedia device" became the Sigma Tel sound card and sound worked great. I think i had to reboot it as Windows got all testy that it wanted to be rebooted. It also might have been because of the Video driver install.. Not sure though. I had something along the lines of three or four installs going at once.
I also think the latest dell driver for your system (XP) works on Vista. I know the wireless driver works in Vista (even though the unit had a 802.11g driver built into vista, i chose the driver from Dell that worked).
Good luck in using vista. You'll see she's a resource hog right away.