virtualdub
open your file in virtualdub
set audio and video to 'direct stream copy' (so it doesn't take ages re-encoding them)
go to start of video, press 'home'.
go to where you want the split, then press 'end'
tap F7 and save it as videoa.avi
then press home (without moving slider yet)
and move slider to the next part and press end
tap press F7 and save it as videob.avi
^repeat for multiple splits