If you previously disabled system restore through the Group Policy Editor,
the option to start it again does not show in the System Properties.
You can re-enable it again by:
  1. Run the Group Policy Editor (gpedit.msc)
  2. Go to Computer Configuration / Administrative Templates / System / System Restore
  3. Set Turn off System Restore and Turn off Configuration to Disable
  4. Right click on My Computer
  5. Select Manage
  6. Go to Services and Applications / Services
  7. Scroll down to System Restore Service
  8. Set it for Automatic
  9. Click on the Start button to start the service
  10. Close down this window
  11. Go back to the Group Policy Editor and configure both to Not configured
  12. Now when you right click on My Computer, there should be a tab for System Restore and you can configure how much space will be used