If you have a huge hard drive and would like to increase the amount of drive space used beyond the "12% maximum" for System Restore, check this out.
1. Goto HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\SystemRestore
2. Look for the DWORD Value 'DiskPercent'
3. The Default value is 'C'
4. You can change the default value up to 'F' which is 15% of your drive or any combination of letters A-F that could allow you to use up to 100% of your drive (if you so stupidly chose.)
5. After you make changes, go check out your System Restore settings and you will notice that you can actually increase the maximum disk space you can use.