Inspired by my trip to Oredev and all the great devices and presentation, I have finally installed Windows 8. I decided to upgrade my Windows 7 installation, and found the installation to be very quick and painless.
After the installation was done, I was asked to activate my Windows installation. However, when I tried to do so from the new Metro app, it just said that Windows failed to activate and that I should try again later.
I entered classic mode and opened the old control panel. There, I found that the old Windows 7 product key was still being used. No wonder the activation process failed. However, I could not change the product key from this view. There was no edit button, no text fields, nothing.
This problem is well-known, though, so I found a cmd command that I could use to change the current product key (why there is no ui for this is beyond me). To do so, start the command prompt and enter the following:
slmgr.vbs -ipk <YOUR PRODUCT KEY>
After this, return to the control panel and run the activation routine again. It should work now.