VMware Fusion - use existing Windows after system reinstall

I've been running a legit copy of Windows7 on VMware. When I upgraded to VMware v6 I was desperate not to have to pay for a new Windows OS. Installed the VMware application - oh no! using the obvious dialogue box it wouldn't recognise the Windows 7.vmwarevm file in the Virtual Machines folder. Eventually I noticed that the Windows 7.vmwarevm file looked potentially active, so I simply clicked on it and everything started working :))

• Click VMware to run it
• Open the Virtual Machines folder that VMware previously made
• Click on the Windows 7.vmwarevm file that looks cheerfully active (or, I guess, any other virtual machine you have previously run).

Possibly this may solve another VMware / Windows problem on another machine where after installing Mountain Lion the virtual Windows claims it is illegal (it is not). (However, I just carry on when it threatens me and it works though looking a  bit messy).