Notes about the VDMK file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The VDMK file type is primarily associated with 'VMware' by VMware, Inc.. It's possible this is a misnamed VMDK file which is the usual file extension for VMware Virtual Disks. However, there are a number of entries in a Google search that refer to this specific file extension for that purpose.