[for Windows 7 read this post]
In my daily work I use a lot of Virtual PC images (VHD) so my host Vista system will stay clean of beta and test software. To get to the files I stored inside a Virtual PC images I normally start the Virtual PC and drag and drop them to my host system. This can be more efficient using the command line tool VHDMount. You mount the VHD and can read and write the files like a normal hard disk in your host system. By importing a small registry file you don’t need the command line anymore and can mount and unmount (dismount) the VHD.
This is what you need to do to mount a VHD inside Vista by double clicking.
Windows Registry Editor Version 5.00[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Virtual.Machine.HD][HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Virtual.Machine.HD\shell]@="Mount"[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Virtual.Machine.HD\shell\Dismount][HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Virtual.Machine.HD\shell\Dismount\command]@="\"C:\\Program Files\\Microsoft Virtual Server\\Vhdmount\\vhdmount.exe\" /u /c \"%1\""[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Virtual.Machine.HD\shell\Mount][HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Virtual.Machine.HD\shell\Mount\command]@="\"C:\\Program Files\\Microsoft Virtual Server\\Vhdmount\\vhdmount.exe\" /p \"%1\""[HKEY_CLASSES_ROOT\.vhd]@="Virtual.Machine.HD"