I've been building some virtual machines in my lab environment, and I've been a bit dissatisfied with their performance. I got some information from colleagues that using SCSI disks is faster than IDE in Virtual Server. Unfornately I had already built the VMs using IDE disks.I didn't want to go through the hassle of rebuilding he VMs so I did some digging and found there's a white paper that tells you how to convert the disks from IDE to SCSI. Enjoy.
http://www.microsoft.com/downloads/details.aspx?FamilyId=8D71F23D-0380-4C2F-81DF-6F96ABE05493&displaylang=en