Just in case you quite fancy being able to mount (and unmount) a single file into your file sytstem and use it as a disk drive, but do NOT want to install Virtual Server 2005 R2.
Download the setup file for Virtual Sevrer R2 SP1 Beta 2 and follow these instructions (from the release notes):
Installing VHD Mount
VHD Mount components are installed as part of Virtual Server default installation at \Program Files\Microsoft Virtual Server\VHDMount. To install only the VHD Mount components, use the Custom option in the Virtual Server installer and clear all components except VHD Mount.
To perform an unattended installation of the VHD Mount components
Extract Virtual Server 2005 Install.msi from Setup.exe by typing the following command:setup.exe /c /t <drive letter>:\<path to the .msi file>For example, to extract "Virtual Server 2005 Install.msi" to c:\SetupFiles, type:setup.exe /c /t c:\SetupFiles
Start an unattended installation of VHD Mount by typing the following command:msiexec /i "Virtual Server 2005 Install.msi" /qn ADDLOCAL=VHDMount
VHDMount is case sensitive.
Big word of warning (thanks to Vern). If you already have Virtual Server installed, performing the above will mess up your installation. You have to upgrade the entire Virtual Server install.