audio and video dont match speeds...

i recently downloaded an xvid... it was split into two files, so i joined them with virtualdubmod, then demux to ac3, and converted ac3 to wav... then i used tmpgenc to make my mp2 and m2v files... i then used IfoEdit to create the vob files... burned with Nero using DVD-R (Verbatim)... and i go to watch it and the video and audio are totaly off, how do i fix this problem??

p.s. in tmpgenc when i am supposed to move the disc space up to 96% it makes the files waaayy to big to fit on a DVD5, so i just leave it... could this have somthing to do with it?