HELP!

Problem:-
In some games after playing for around 5 min starts to run slow, and jittery sound occurs. It never crashes, just slows down to an unplayable framerate (or sometimes speed)
Hardware config:-
Assus A7V133 motherboard
Athlon thunderbird 1ghz
Assus Geforce 2 MX with tv out (no in)
Creative Vibra 128 (might be cause of problem)
Netgear 10/100 base tx networkcard, Model FA311
RAM: 192meg, 1*128, 1*64, both PC133

Other:
I have just noticed that DMA 1 and 5 are missing in system infomation, they are both required for the soundcard. (1 for 8bit sound 5 for 16bit)

UPDTAE:
the manual says that in windows, DMA are not needed(but are in DOS)

done! didn't work