Usually when you have sync errors, it's not a matter of simply stretching one to match the length of the other. The typical reason for sync errors is frames were dropped at capture, but ONLY the video portion, the audio did not drop.
ATI MMC, for example, will drop BOTH if one drops, which is smart. It may sound as bad as it looks, but at least it's in sync.
Software like PowerVCR II or Mainconcept
tends to drop just the video, and you have these horrid files that can never be put in sync again, it's "impossible" due to the time and knowledge it would take.
If it really is simply a matter of stretching the audio, an NLE is what you'd need. Something like Vegas Video or Adobe Premiere is in order. However, it cannot work very well with MPEG, so you would need to convert the MPEG back to a raw uncompressed AVI, using a freeware tool like VirtualDub
(the one that can read MPEG) and save a new AVI. Because you're going to an uncompressed AVI, no quality it lost.
When you fix it in the NLE, you will then have to re-export the video as a new MPEG file. Some quality may be lost here, but if the source was high quality, it should be minimal, likely transparent, especially if you use a good encoder like MainConcept
, CCE or Procoder.