Does defragmenting the system multiple times in a row help the system run more smoothly?

From my experience, the answer would be no. The only circumstances in which defrag makes any noticeable change in system performance is if it's an old Windows 98 computer with a small hard drive that is almost filled to capacity. Just so you know, I'd consider small less than 10GB. If your system has Windows XP, you're pretty much wasting time by running defrag. It will probably do it's job of moving fragments back to their appropriate space on the disk, but you'll never even notice the difference. :) Goodluck!