How can I mount Vista .vhd file on Windows 7 RC?
Launch Computer Management and right-click the Disk Management node - select Attach VHD, browse to the file and click OK.
As for booting vhd, you can only do that with Windows 7 or Server 2008 R2 vhds.
Note that Virtual PC VHD's are incompatible with Windows 7 VHD's. Nobody has provided a good explanation as to why. But therefore you can't create one in VPC and boot to that, either.
Kinda sucks, cuz I wanted to boot to the .NET 4.0 CTP VPC VHD and couldn't for that reason. If you created this VHD with VPC, good luck.