Windows 7 installation: The product key does not match current Windows SKU

I just finished installing Windows 7 on my iMac, I had no problems during the installation until I got to the product key part, I grabbed a new key from the MS site, only to find out it didn't work, then I tried with another key, no luck, long story short, I tried at least 5 keys, including one I had already used to install it on my laptop, none of them worked.

Google has very few links to people who have had the problem, and the only answer seems to be that you may have downloaded the checked build, and you need to chose the Ultimate version; I had chosen Business edition.

Chris responds: You are probably installing from the "checked" ISO image. Please choose "Ultimate" and your key should work.

However, when you are on that screen there is no way to go back, do I don't know how you would select Ultimate.

Anyway, the solution that worked for me was to simply leave the field empty, yup, that simple.

So, if you downloaded the checked build, chose the Ultimate version; if you're stuck in that page, I hope this helps you