xp will not boot

I woke up this morning and my system will not boot. last night i scheduled a boot time defrag using diskkeeper to run this morning.Now after xp runs a chk disk it restarts xp then locks up.i tried manually restarting and the same thing occurs.Xp hasbeen activated, and has ran fine for a long time.The only thing i did differantly was set up the boot time defrag. I would like to get it up and running without a reinstall of windows any i deas will be appreciated