Is it normal for a computer to take more than 13 hours to defrag?

It really depends on how badly fragmented the hard drive was. Most computers with Vista are pretty slow unless they have tons of memory. I recently ran defrag on my mother-in-law's computer and it probably took around that long (I started it and went home so not sure). It was an extremely fragment Dell with about 3 gigs of ram. I generally run Ccleaner from CCleaner.com before I defrag to get the junk out before hand.