Win7 Activation Key

mr.elmo01

Prominent
Nov 12, 2017
1
0
510
I installed a legit Win7 Home Premium on my PC, but I lost the activation key. My PC keeps saying "Activate Windows now" and I get popups. If I buy an activation key from ebay or something, do I need to reinstall my Windows or can I just put the code in and I'm good to go?