The only PerfectDisc I know is a defragger, which is probably continuously monitoring the drive and dynamically defragging it. If you can't find the program go to run (start menu) type msconfig and look for it in the startup section. If you find it there, disable it, reboot and try again.
If that doesn't help take a look in the task manager in the processes tab, if you can see it, highlight it, end the process, then try installing again (without a Windows restart of course, otherwise the defragger will be reloaded again).