One customer reported having problems taking snapshots of a Windows 2008 R2 VM, and the issue seemed to boil down to an ADAM writer installation/registration problem. (See

Actually, VMWare said the problem was caused by “a hard-coded variable (SYSTEM) in the comreg.exe provided with the vmware-tools installer.”. As a workaround, they provided me with a modified version of the COMREG.EXE tool.

A related problem is that VCBRequestor.dll file is not installed by the VMWare tools installer, so I’m providing both the COMREG.EXE and VCBRequestor.dll files in this ZIP archive.

Here’s how to proceed:

1. Download the ZIP archive and extract it somewhere convenient. 

2. Replace the existing COMREG.EXE in C:Program FilesVMwareVMware Tools folder within the virtual machine with the downloaded file.

3. Copy the VCBRequestor.dll file from the ZIP archive to the C:Program FilesVMwareVMware ToolsDriversvss folder.

4. Manually register the VMware Snapshot Provider service:

a. Launch an elevated command shell (Run as Administrator).

b. Enter the following commands in sequence:

regsvr32 “C:Program FilesVMwareVMware ToolsDriversvssVCBRequestor.dll”

regsvr32 “C:Program FilesVMwareVMware ToolsDriversvssVCBSnapshotProvider.dll”

“C:Program FilesVMwareVMware ToolsCOMREG.EXE” -register “C:Program FilesVMwareVMware ToolsDriversvssVCBSnapshotProvider.dll” “VMware Snapshot Provider” “vmvss” “VMware Snapshot Provider”

5. If you see the error 80110801 when registering the COM application, you must delete the VMware Snapshot Provider COM application. To delete the VMware Snapshot Provider COM application:

a. Click Start > Programs > Administrative Tools > Component Services.

b. Double-click Component Services > Computers > My Computer > COM Applications.

c. Select VMware Snapshot Provider and press Delete on the keyboard.

d. Follow procedure under Step 2 to manually register the VMware Snapshot Provider COM application.

After that, quiesced snapshots can be taken without the usual I/O time-out error message.

I hope this helps others solve this annoying bug.