For the Windows Vista Service Packs there was vsp1cln.exe (SP1) and compcln.exe (SP2) to cleanup the backup files created during the Service Pack installation. For Windows 7 Microsoft did not provide a separate cleanup tool, but instead leverages the windows-build-in DISM tool.
To remove the backup files created during the Windows 7 Service Pack 1 installation run the following command from an elevated command prompt.
dism.exe /online /cleanup-image /spsuperseded
After successful completion you should get some disk space back.