Try changing the guest virtual machine type to Windows Server 2008. If that doesn't work, make a new virtual machine and go into the settings for the new VM. Delete the new virtual disk and tell it to use an existing one, and navigate to the old VM. A VM is actually a folder containing the configuration, the virtual hard disk, and other files similar to a Mac OS X application, so you should be able to navigate inside the VM file through VMware's file open dialog. If not, right-click on your old VM, choose "Get Info" and remove the file extension ".vmwarevm." The VM will now appear as a folder in Finder.