Using Vista Home Premium 32

System Restore is not working in any of the options. I can't remember the exact message, but after running the program it says it was unable to complete restore and then offers the option of trying again. When the option to select another restore point is offered the same thing happens. If I select 'undo' restore then again I get the same message after the program has run - in all cases no changes have been made. Any suggestions or advice please?