I too have just purchased the VP-MX20 with bundled Mediashow 4 software and am having the same 'aspect ratio' problems.
I have spoken to Samsung technical who blame the software. I will be emailing Cyberlink tech for a response to specific questions.
Firstly let's face it, I paid £117.49 for a brand new SD camcorder with 34x optical zoom, quite a few features, and reasonable picture quality; so I would not expect to get an all singing all dancing machine/software for that money. Having said that the software is a bit naff, but maybe tech's answer will improve that. I personally have had no problems loading the software (Vista) nor updating it with the latest versions, despite my machine spec not being upto their 'minimum' standard.
From playing around with the camcorder and software I have deduced the following:
Irrespective of the shooting ratio (16-9 or 4-3) the camcorder stores the image in 5-4 aspect ratio. (Samsung for some unknown reason love 5-4 and most of their monitors were/are? 5-4) This is why when downloading the video to the software it seems to be 'squashed'. However if you make a DVD of the video and play it back on a TV and select the aspect ratio on the TV you recorded in, it plays back perfectly. This is the same as playing the video from the SD card through the camcorder.
My problem is with the software not chaning the aspect ratio when writing out to a WMV/MPEG2 file. It does give a black box in the selected mode (16-9 or 4-3) but the video does not fill the box as it maintains its 5-4 aspect; which makes it distorted when playing back through a PC. Hence my questions to Cyberlink.
I will be playing around with it over the next couple of weeks and if I get any more info I will update.
regards, Norman