Manual activation of Windows 7 - Control Panel>All Control Panel Items>System
At the bottom of that window you'll see the Windows Activation status. If the status is "not activated", click the link to “Activate Now” and follow the wizard.
Or from the command line:
Start>Search Box>type: cmd
When cmd appears in Results above, right-click it and choose "Run as administrator". Provide the password/OK to the UAC box and an elevated command prompt will open. At the command prompt type:
slui [enter] - which will start the Activation process.
MS-MVP - Elephant Boy Computers - Don't Panic!
FWIW, it's possible to runs SLUI direct from the Search box - you just have to accept the UAC prompt along the way, once you get into the Activation Wizard.