How to license P2V OEM Windows 7 with a retail license with VMware Fusion?

A friend of mine did a P2V of his Acer physical Windows 7 Home Premium to run on his Mac using VMware Fusion.

Now the VM complains it is not properly licensed. Microsoft is directing him to Acer, and Acer to Microsoft.

In the mean time, he bought a new retail Windows 7 Home Premium License and Media, but doesn't want to reinstall his machine. However that license does not work; he gets a Dutch message (that has an error code 0xC004C008 when going to "Details") which I've tried to translate.

• Dutch
  • Geef een andere productcode voor activeren op.
    De opgegeven productcode kan niet worden gebruikt om Windows op deze computer te activeren.
• English
  • Enter a different product code to activate. The entered product code cannot be used to activate Windows on this computer.

What ways are there to get this machine properly licensed?