If you have System Restore enabled it takes up 10-12% of your hard drive space. If you have limited disk space, removing old or unwanted restore points will give you back precious disk space.
Click "Start" and go to "Control Panel". Open "System" and go to "System Restore". Tick "Turn off System Restore" and click "Apply". All previous (automated) restore points created by your PC will be deleted. When it's done remove the tick mark and click "Apply". Close all windows.
Go to "Start", "All Programs", "Accessories", "System Tools", "System Restore". Create a restore point and label it as "Stable System". Now you only have 1 restore point taking up a small space in your drive.