Okay, again - that refers only to the system drive / partition (c:). Any data on a separate drive or partition will not be touched. If you are concerned though, you can do one of several things: copy critical data to off-disc media (cd, dvd, usb drive, external drive, etc), use a disc imaging utility to image your z: drive, or use a backup utility to copy your data to a backup file off disc.
But as I said, the restore utility will only effect c: drive.