I am running Raxco FD-ISR and just installed Perfectdisk 8. Analyze asked for offline defrag. When I attempted, upon reboot, a blue screen came up stating that it could not access the C drive. Then it rebooted. When I tried to go back old snapshot with Perfectdisk 7, the computer would not boot. I will have to restore with Acronis True Image. Beware of Perfectdisk 8!!