I am running Win7 Home Premium without any problems; however, I have acquired Windows 7 Professional. My question is how can I use the license for the Home Premium on another system? I know I would have to call Microsoft to reset the key: but when would I do this?
If you have the retail (not OEM) version, you should have no problems. Go ahead and try to activate the new copy of Windows, and if it doesn't work, call Microsoft, and explain the situation.
MS is only checking to see that you don't have the same license installed on more than one computer. If you attempt to use a key that has already been tied to another machine, it will normally require a quick robo call that trades a series of numbers which are essentially disabling the license on the old machine and tying it to the new one.
You only have to speak with a person if this process has been repeated an unusual number of times within a given time period, but as Jon says they accept any explanation which they then verify.
I reinstall OS all the time but have never had to speak with a MS person, just the numbers machine. However I keep all my documentation (including upgraded OS key trails) to be sure.
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