|First off, you can't "downgrade" from 2k3 to 2000. You can install 2000 after wiping 2k3. |
Actually, now that I think about it, you can do both at the same time (ie: wipe 2k3 and then install 2000). To do it though, you need to boot from the 2000 CD. If you're not booting to it, then you need to go into your BIOS and change the boot order so it boots to the CD before booting to the hard drive.