watching films

I have a problem on my Acer 505 travelmate laptop that has buged me for weeks
during playback of movies in Dvd mpeg or avi format the film im watching freezes up and the computer shuts down and restarts
perhaps i should start at the begining
becouse my laptop never came fitted with a dvd i bought an archos mini dvd player which is conected though the cardbus
or pcmica socket and my problems started
I emailed Acer and archos support who both ignored my requests for assistance since which time i have tried every updated driver and player i could find on the internet with no change
hardware manager shows no conflicts and watching vcd's via the cdrom has no problems
my o/s is windows 98
can anybody help please - its driving me nuts

 

thanks for the reply
I have checked the memory settings which look ok to me but dont realy understand enough to attempt changing them also when i have tried i am asked to restart computer for settigs to be changed and they come back the same - or without some sort of software which i have been unable to find - and none show any conflicts
i have tried enabling and disabling DMA I have also disabled my antivirus scanning also tried removing it completely also other programs realated to my laptop for example laptop manager-safeoff-etc i also tried installing windows 98 from my windows 98 second edition disk and adding the drivers for onboard hardware instead of from the Acer recovery disk all with no progress
also got all the latest codecs and updated direct x and windows media player

 

update

for anyone following this i have found that disableing the sound driver a crystal audio codec i can watch anything the whole way though (but without sound)
showing no conficts in windows 98 system manager
both problem devices my external cardbus dvd and sound card are on IRQ11
i have tried to change the resorces of both but restarting just freezes the computer
HELP PLEASE