You receive an access error message when an application calls the StgOpenStorage method on a Windows Vista-based computer
When you run an application on a Windows Vista operating system as a user who is not an administrator, you receive one of the following access error messages when the application calls the StgOpenStorage method:
Windows Vista Service Pack 1 (SP1)
This problem occurs if the program process impersonates a user who is not an administrator.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB950106.