One of my wifes friends (from work) ask me why he can't defrag his HHD ? It starts gets to 2% then shuts down ? Win/98 system!

I told him I wasn't sure as I have Win/2k Pro. &
Win NT4.0 on my systems, and my wifes win/98se has no problems w/defrag.

Is this a comon problem with win/98? and maybe he should download a defrag utility? any Ideas on the problem or advice on a defrag program?

Thank you in advance for any help!