I just brought a mp3/vcd player (napa 311-model). I also have "nero cd burner" and nero expres. With the Nero MPEG-2/SVCD encoder I can burn video files to SVCD and watch them on all SVCD compatible DVD players. My questions are: 1.how could I convert a movie from ntsc to pal, and 2. could Napa read subtitles (.sub) files. If not, how could i "stick" the subtitle to movie ?

I am familiar with your portable as I briefly owned one before I returned it because it didn't play CD-Rs very well. I can give you a few tips. VCD portables do not play SVCD. Remember, these are DVD players. They are VCD, MP3 and audio CD players. They don't support MPEG-2 video at all. VCD does not support selectable subtitles. To use subtitles in VCD, you must make the subtitles be part of the video image - that is, they are always "on" and can not be turned off. I found the Likko J4 model
(see http://www.lik-sang.com - the only place I know that sells it) to be the best of the portables, but it does not support CD-RW at all. I had a discussion on another forum with a guy and it seems that the portables are kind of shaky on playing VCD on CD-R. The Likko J4 did it best and even it was not perfect. It may depend on your burning program (Nero seems to be no good for the portables, so maybe VCDeasy is better) and your media. I tried using TMPGenc to convert a NTSC DVD to PAL VCD and the results were awful. Totally unwatchable due to jerkiness in the picture. Some of the guys here have talked about a fairly new software product that does a good job of PAL<-->NTSC conversions, but I don't remember the name.

Procoder does reasonable PAL<->NTSC while converting from avi to mpg.

aDVanced converter will convert PAL DV avi to NTSC DV avi, and visa versa, but less appropriate perhaps since you'll then be encoding to mpg from a second-generation avi file (not that it would matter much if the end product will be VCD)