You experience problems when you try to mount VHD files by using the Vhdmount.exe tool after you apply update 948515 in Virtual Server 2005 R2 SP1
You apply update 948515 on a computer that is running Microsoft Virtual Server 2005 R2 Service Pack 1 (SP1). After you do this, you experience problems when you try to mount Virtual Hard Disk (VHD) files by using the Vhdmount.exe tool.
For example, if you run the vhdmount /m vhd file command or the vhdmount /p vhd file command, you may receive the following error message:
The specified operation could not be completed as an unexpected error has occurred.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB953482.