I had this same problem with a Geforce3 TI500. The howling sound happened
every morning on bootup and gradually the duration of the sound got longer
and longer. This went on for a period of months and then began happening
intermittantly throughout the day. That's when I got in touch with Dell
support and they sent me out a new card (GeForce4 TI4600) as a replacement.
My computer was purchased in January 2002 and covered under extended
warranty.

BEK