hi, lately i have been having the same problem on my computer. a dell dimension, fairly old. to be specific, about 3 - 4 years. the dell is running with 500mhz and 768 ram, and a nvidia geforce 4 64mb.
well i used to have fine dvd playback, no problems. but then i switch in a hard drive from another computer. before i do anything, i format and install 98. i install all of the neccessary drivers, all up to date. i download 2 different dvd programs ( which include dvd decoders ) and i enabled DMA on my dvd drive. and yet, it still plays back choppy, and it isn’t like a random choppy playback. it’s a constant thing.