Can I "convert" my Windows 7 Ultimate Edition (RTM) to Enterprise Edition? [duplicate]

"It is not possible to ""downgrade"". In fact you would hardly be doing a downgrade on this case. Windows 7 Enterprise is just like Windows 7 Ultimate. The difference is that Enterprise can only be activated with a volume license MAK or KMS key. Windows Ultimate, on the other hand, is activated through the normal means.

If anything, you would be upgrading your Windows 7 Ultimate single license to a VL. But since the windows versions are hard-wired to their activation mechanism (you don't even access the same activation servers or use the same activation code), I can't see how you could do this. And a reinstall is unfortunately necessary."

There is no functional difference between the Ultimate and Enterpise editions. It is pretty much just the activation and licensing mechanism that is different. If you have a valid MSDN subscription then the simmplest thing to do would be to just use the MSDN website to generate an activation key for Win7 Ultimate. If you do that, then you don't have to face a reinstall.