computer freezes up at boot

windows 98 se updated properly
using windows media player 9
acdsee 4
whenever i try to view a mpeg file windows media player
freezes due to bad quality
also when u do a right click acdsee 4 allows to view a
preview of the movie
when the movie hans in the preview the os also freezes
when the computer is restarted it give a windows
protection fault and shuts down the computer
when the computer is booted again the computers freezes
at the point where the taskbar is about to get loaded

the normal funcionality is resumed only after keeping the
computer shut for atleast an hour.

other system details are
pentium 3 833 mhz
riva tnt 32 mb agp card
20 gb hard drive