When you say accesses the floppy.. Do you mean you can hear it being accessed when you start a defrag? If so then thats normal.. Mine does the same and i think the only way for you to stop it is to disable the floppy in the bios..
I'm assuming you almost never use the floppy drive anyway? Either way, just go into 'Device Manager' and disable the floppy from there. If you disable it in the bios then you would need to reboot and reactivate it if you wanted to use it. Disabling it in 'Device Manager' will prevent random seeks of the drive, and then it only takes a minute to re-enable it if you need to, without a reboot.