It looks as if you have backed up your C drive to your C drive! Old contents 74GB + BackUp 74GB + Space left 9GB = 153GB, which is the approx size of your drive. I know it's a 160GB drive but it's true size will be a bit smaller than that.
Have a look at the contents of your C drive and you will probably find the answer.
System Restore is notoriously unreliable and only works when you don't need it! IMHO.