WIN7 Registration removed

Hi all. Just installed Win 7 developers edition with ubuntu on an external usb drive. Runs great with no problems.I do however have a problem now - it has removed my registration with MS and states I am not registered. Can anyone give me some advice about this grief - I do not want to remove the boot loader. Thanks
Any reinstall of a single-use EULA Windows on a new device will trigger re-activation.
If you activate the new copy within the 30 day trial, the old version automatically becomes invalid (a "pirate" copy, no longer legally usable).
The EULA does not allow two working, legal copies of the same OS.
Decide which one you want and activate it from control panel > system.
Activation should get automatic validation, but if not, just phone the free MS number and ask for a manual validation key. Explain that you've moved the OS to new hardware.
(btw If it's an OEM copy of the OS, you can't move it to new hardware, though they'll normally accept a HDD replacement provided that the mobo, graphics etc are unchanged)