Trouble Syncing Audio and Video When Converting Videos

I have a lot of devices that require video converting(cell phone, ipod, psp, etc.) and every time i convert a video, the audio is not in sync with the video.

I have used A LOT of programs for converting video. I would say about 20-30 programs, and some were not free. =/

But still the audio is off from the video.

So I am starting to think that i am doing something wrong. So someone please help me with these problems or point me to a program that syncs the audio and video together flawlessly.

Thanks,
Poison 47