Windows Upgrade Help and more

Agreed. And just to be sure, have you checked Task Manager to see if a specific app or process is using high CPU or memory when the slowdowns happen?

That error usually means the activation servers are having trouble verifying your license after the upgrade. First, make sure you're connected to the internet, then open an admin Command Prompt and run "slmgr /ato" to force activation. If that doesn't work, you might need to use the Activation ...