NT Memory dump on shutdonw

I may have sent this question twice. My apologies if that happened.
I have an Windows NT PC with sp5 installed and it has been working fine for the last 6 months or more, now suddenly in the last 2 weeks, the user gets a memory dump when he goes toshutdown his pc. This has happened at least twice in the last 2 weeks.
Question: How can I avoid this happening and what issues should I be addressing to resolve this problem. Is it a warning of future trouble?
Thanks Claudette