Used that to test encode on my PC (Windows Vista 32bit, Core 2 Quad Q6600, 3GB DDR2). And here are the unscientific result:
Original File: [CoalGuys] K-ON!! S2 - 04 [C766BBA9].mkv; 1280x720p, 242MB.
Using HTC Touch HD Video Converter v1.21 (aforementioned in the quote):
.mp4; 800x480 (with thin black bar on top and bottom), 126MB, Took 30 minutes to encode, subtitle has been turned into something generic, larger sized font, and my PC sounded like a jet taking off... really loud, felt like it was going to pass out.
Using Winnydows' Xvid4PSP v5.037 (my favorite PSP converter):
.mp4; 800x448 (correct aspect), 129MB, took 17 minutes to encode, subtitle font and size has been preserved, and my PC sounded pretty loud, but not as loud.
Neither produced any sync error or noticeable artifact on video. I picked out something with subtitle to make sure that both were able to enable subtitle as it should.
So... I think I'll stick with Xvid4PSP. If you feel adventurous, here is the link:
XviD4PSP - Video software and downloads - VideoHelp.com
Be sure to change "Format" to "MP4", drop the file you want to encode, then go to
Video -> Resolution/Aspect -> Change the "Output Resolution" to 800W, then keep "Input Aspect" and "Output Aspect" to be same. That will adjust the height accordingly. Press "Apply", then "Ok".