Just thought I would offer this tip. Once you’ve installed SP1 and everything is running well, AND you are absolutely 100% sure you do not want to uninstall it, AND you have backed up your system…
You can run this command vsp1cln.exe. This will allow you to reclaim significant disk space.
To do this press the Windows + R keys and type vsp1cln.exe in the run box.
or if you prefer using the command line:
press the Windows + R keys and type cmd then type vsp1cln.exe.
More info from Microsoft:
Windows Vista SP1 File Removal tool (Vsp1cln.exe). Vsp1cln.exe is an optional tool that you can run after you install SP1. This tool removes older versions of components that have been updated in SP1, which are stored during the installation in case you need to uninstall SP1 later. Saving these older components increases the amount of disk space that is used. Typically, you should run Vsp1cln.exe if you want to reclaim this disk space after applying SP1 and if you will not need to uninstall SP1. Note, however, that you cannot uninstall SP1 after you run this tool. You can use this tool both online and offline, but you must have SP1 installed and you must use the correct version of the tool. If you are running this file on an offline image, you should use the Vsp1cln.exe included in the Windows OPK or AIK. However, if you are running this file online (on a computer that you are booted into), you should use the Vsp1cln.exe file located at %windir%\system32\vsp1cln.exe.
Please do not whine at me if you run into problems and you haven’t backed up your computer!