best program for generaly converting movies would be adobe premiere. best video editing program, for the pc, out there. and before any smart ass hops in, avid sux without out the hardware system setup for it and final cut only works on the mac (and I still think it sux).
best program to add in audio to a movie file would be premiere or after effects. after effects if you really wanna fuck with the audio. if you are just going to lay down audio tracks then premiere is a good way to go.