cannot boot after defrag pos OS selector install

after installing OS selector from Disk director Suite 10 ( worked fine every time i used it) I did a defrag and later XP did not boot up. Solved this problem by booting from Disk Director Suite 10 cd. It did take two tries (restarts) before xp finally booted up. now still fine. I defrag in safe mode only with 2 defrag passes to get best results. Unfortunatly I had the (bad) idea that 3 defrags would be better than 2. Big mistake due to (I think) too much rearranging of MBf to an unrecognizable location from XP's view point. I believe this method will work after any defrag caused hang ups.