If your computer is displaying an error that Windows needs to be activated, follow these steps:
1. Connect to the Columbia University network through the VPN (instructions here).
2. Click the Start Button
3. Right-click "Computer"
4. Select "Properties"
5. Click "Activate Windows now"
If that activation doesn't work, please follow these instructions from CUIT: https://cuit.columbia.edu/windows-7-activation