There are 2 ways to do install it onto a driver other than C:
Change your registry *prior to installation* to set the ProgramFiles directory to a different drive. The relevant registry entry is: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ProgramFilesDir
2. Use the unsupported AttachLibrary tool to allow the specification of a directory other than the one being used for all MSDE databases. 我推荐第一种,很不错