Since staring at Microsoft I work a lot with VPC’s (Virtual PC) and that really bloated my hard drive. Found this post by Roy Osherove addressing this issue using differencing virtual hard disks. Really neat!
The basic idea is that you install a base-disk (for example base_Win2003Sp1) and then extend it with differencing disk for different Visual Studio/SQL Server versions or what ever you’re up to. The initial gain won’t be great but it will increase with every new vpc installation.