I run the above on a windows 7 64 bit PC. I back up onto an external hard drive twice a month and, following the first back up, only new files are backed up each time and this has worked for many months. I have tried to back up this month without success, it appears that my PC is trying to do a full back up again and, no matter how many times I try, I am unable to start an incremental back up. Has anyone any ideas pleas?