I recorded an HDTV movie with 1080p resolution, and it seems it has got this weird 50fps framerate. Understandably so, since its a PAL broadcast. But my problems now are:

a.- Playback is jerky, even on my quad-core laptop
b.- Audio and video are out of sync.

How can i stitch this up? Is it safe to downconvert it to 25fps so that it plays normal, without missing any significant information?
What's the best way to delay the audio to the appropriate amount of mseconds so that it synchs itself?

P.S. On my old junky laptop it plays more smoothly than the newer i got recently. Maybe its some kind of a codec issue? But i also tried standalone media players such as WD TV Live (last gen.) and my PS3 gaming console, and both of those have stuttery playback...