What happens if you don't activate Windows?

Ok, really dumb question and it's probably been answered somewhere, but I couldn't find it by searching quickly.

My dad basically installed a Windows 7 Ultimate with the key I happened to have used on my PC. Now, Windows is both installed and activated on my PC, but my dad didn't activate his when I told him the key was used on my PC.

My question is simple, will MS basically disable or somehow cripple my PC since it will eventually notice that 2 computers are using the same Windows on the same key(albeit one not being activated)?

I mean, it wasn't intentional and I'd hate to have to re-do my PC because of a mistake my dad made by picking the wrong CD >_<

 

It will not deactivate but it is not legal either.

 

just a heads up your dad wont have to reinstall all over again. he should be able to right click the my computer icon and choose properties. On the next window if you scroll down it should say change product key. he can then input the other (legal) key you have.

 

Or you can run Command Prompt with Elevated Permission
C:\Windows\System32>slmgr -ipk ENTER-YOUR-OTHER-LEGAL-KEYS
Wait for a while after entering the keys for Windows to verify it.

 

Well I know he can change the key, I just wanted to make sure Microsoft wouldn't deactivate all Windows OSes using that key if the activation time went out on one of them(because I happen to have used and activated said key on my PC).

I'll tell him to change keys anyhow as we have lots of them lying around. Just didn't want my PC to be non-functional before I did that you know? >_>

 

Microsoft doesn't deactivate key I think.

 

Um, yes they can and they will.

Generally keys that are sold on ebay that are sold from a TechNet or MSDN account are the ones they blacklist once MS realizes those keys were sold against EULA/TOS.

 

It's not a sold key though, and it's neither MSDN nor Technet, it's a promotional key. My dad just used a wrong key, I told him to change it sooo.

 

should be running on RFM(reduced functionality mode)
how many days passed since your dad's computer hasnt been activated?