Also deleting all restore points bar the current restore point with "Disk Cleanup" is good maintenance as well,as malware can hide in restore points, as more free space is gained.
You can delete Restore Points without using Disk Cleanup (cleanmgr.exe). Just go in the System window, go in the "Advanced System Settings", and under the "System Protection" tab, you have a "Configure" button you can press. From there, you can delete all your Restore Points by clicking on "Delete" and also decide of the maximum size allowed for the System Restore service.