Windows 7: Activation Question

I was able to obtain a legit copy of windows 7 pro and key via my university infosys course, who were involved in the development and testing of the software. Initially when I installed the OS activation worked fine, however a month later I was unable to use the OEM keys on a different machine, so I'm guessing they were leaked and MS blocked them.

My question is, now that I've reached the deadline for activation, am I able to activate using a purchased OEM key from a legit online reseller for the same specific version of the OS (i.e. Win 7 Pro), or is the key specific for a particular installation and will I have to reinstall everything?

OEM is locked to one machine for life. If you purchase another OEM key, you can put it on a machine, but then again, you cannot use it for another machine.

Thanks, that's all i needed to know

If you are already activated with a key, you would have to reinstall to change the key.

Nope, not activated with any key, just trying to avoid re-installation for the sake of activation.