I have a Dell Inspiron 15 (3551). The hard drive needed to be replaced and reinstall Windows 8.1 from a USB. Now Windows is not activated. How do I get the activation key from Dell since I can't find my original papers from my laptop? I am not able to connect the laptop to the internet as well. I assume it's because Windows 8.1 is not activated. Can anybody help me?
There will be a phone number on the activation screen - call that and tell Microsoft you replaced the drive. They'll activate the copy.
Windows not being activated does NOT prevent you from getting onto the Internet. You probably need to install wired Ethernet and/or WiFi drivers.