The original version of Windows Vista is no longer supported by Microsoft. To get support from now on, you will have to be running Vista Service Pack 1 or Vista Service Pack 2.
When you install Vista SP1, the installation procedure leaves all of the pre-SP1 files on your system in case you need to uninstall it. After update to SP1 you cna see the files listed in Programs and Features on the Installed Updates page.
these files, which are required to allow you to uninstall SP1 and revert back to the original version, can take up a large amount of hard disk space. In fact, the files can take as much as much as 800MB.
To remove all the leftover files and reclaim some valuable disk space by using the SP1 Files Removal Tool. Fortunately, this tool is automatically installed on your system as a part of the SP1 upgrade procedure
Be 100% sure that your system is functioning perfectly with SP1 before you run the SP1 Files Removal Tool
For detailed information on how to remove SP1 from your system and revert back to the original version in the Microsoft Help and Support document “How to uninstall Windows Vista SP1 as a troubleshooting step.”
