Fix for problem with edits and better instructions
For those of you still struggling with getting this to work properly, with a bit of searching and trial and error I finally got it to work. When I installed Parallels 8 and Windows 8 it seemed to work fine, until I had to update Windows and then realized it didn't activate properly when it was installed.
Ok, to clarify the earlier post by the user above is correct for the most part. Using my new Imac with Mountain Lion, and my newly installed Parallels 8, I thought it would work fine since I bought a full retail version of Windows 8.
I found it a bit confusing to navigate in Windows 8 within MacOS, but here we go a more detailed explanation and step by step to fix this problem.
1. Open regedit by pressing Windows-R <<< it's R (not Q as mentioned earlier, R stands for Run command). (which if you have an iMac means you hold down the COMMAND button and the letter -R) entering
regedit and selecting the result from the list of hits.
2. Navigate to HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/Setup/OOBE/
3. Change MediaBootInstall from 1 to 0
You do this by selecting the item "MediaBootInstall", click on it, and it will highlight, then you can type in '0' as the value, hexadecimal or decimal doesn't seem to matter.
4. Go back to the start screen and enter cmd there.
Note: To get back to the Windows 8 start screen, you just hit "COMMAND" key on your iMac keyboard
Then yes, you just start typing "cmd" and on the screen you will see command prompt appear as an app icon
5. Right-click Command Prompt and select to run it as administrator.
If you highlight the command prompt icon and then right click it, then at the bottom of the screen you will see the option to run as administrator.
6. Type slmgr /rearm on the command line and hit enter.
Now you're almost there! If you then type at the command prompt: slmgr /rearm
and then hit enter, it should return you to the command prompt.
Exit out of the command prompt window.
7. Reboot Windows now.
You reboot in Parallels, by shutting down the Windows 8 VM. On your bottom left you will see the option to shut down and do that. If you did this correctly, the next time you open Parallels it will say Windows 8 click to start.
As noted above by the other user / member, if you already installed Parallels with your Windows Pro 8, then you don't need to do anything else, it should be already activated.
Go to:
Control Panel > System and Security > Action Centre > Windows Activation
and you will see that it is properly activated. To find Control Panel, hit the COMMAND button again (which is equal to the Windows button) and then just start typing Control Panel and then it will show up.
Windows 8 is interesting in that you just start typing from the start screen to find the things you are looking for, so it's pretty intuitive, but it would have been nice to have at least a shortcut page so you have a chance to figure it out without googling all this information.
Hope this above information helps save someone else alot of time. I know that alot of the instructions out there are pretty vague, but I wanted to fill the gap by helping out.
Cheers,
