Windows 7 won't activate

I just replaced a hard drive on a Win7 machine, cloning the old drive to the new one, and it boots up fine, but tells me that Windows is no longer activated. I go through the process, but each time it tells me that the KMS server is unavailable. This machine was never in a "corporate" environment, so I don't know why it's doing this.

Is there a way (preferrably without reinstalling Windows!) that I can "force" the KMS stuff to go away, and activate directly with Microsoft? I have a valid key, just no way to activate.