Reclaim Disk Space after an XP Hotfix Installation
To reclaim diskspace from Hotfix installations, you can use a freeware:
this utility removes Hotfix Backup files and the Add/Remove Programs Registry entries.
Reclaim Disk Space after Vista Service Pack Installation
For Vista SP1 you may use the File Removal Tool Vsp1cln.exe from the command line.
For Vista SP2 you may use the File Removal Tool compcln.exe from the command prompt.
Keep in mind that once you have run these tools, the Service Packs cannot be uninstalled.
You may also refer to the Microsoft article about the Windows Installer Cleanup (MSICUU2.exe) utility.
Reclaim Disk Space after Windows 7 Service Pack Installation
For Windows 7 SP1 you may use the Disk Cleanup Tool and use the Systems Files Cleanup option:
Alternatively, you may also run (as administrator) the command line:
dism /online /cleanup-image /spsuperseded
To save even more disk space, you may also cleanup obsolete restore points in the Other Options menu: