You can regain about 3GB of Drive Space by removing the backup files after SP1 installation. Removing Windows 7 Service Pack 1 Backup Files
The easiest way to remove the backup files of the Windows 7 Service Pack 1 installation is the following. Open a command prompt as administrator .Click Start => Search, type 'cmd' which will propose you the icon of the black DOSbox, a right-click on it and select "Run as Administrator". Use the following command to free up disk space after the service pack installation:
dism /online /cleanup-image /spsuperseded
The process takes a few minutes to complete, it’s not done when it says 100%. Wait til you see the sentences “Service Pack Cleanup operation completed. The operation completed successfully”. Please remember that you cannot uninstall the service pack after you have cleaned up the disk space.