I've noticed some confusion as to whether the TH55 can play MPEGS natively and after a couple days of experimenting I finally was able to make it work.
Thought I'd post this to help clarify the HowTo part
1) Click on a MPEG file in Netfront and when it asks to open or save, select "Save"
2) Netfront will download the movie to the MStick into the "/Palm/Images" directory.
3) Use Clie File Explorer (Very important) to create a new Root directory on your Mstick called "/DCIM/100MSDCF"
4) Move the MPEG you just downloaded (ie> test.mpeg) into the "/DCIM/100MSDCF" directory.
5 Lastly, rename the MPEG using this format... MOV00001.MPG
example--> I renamed test.mpg to MOV00001.MPG
*** Very important***
The extension ".MPG" is case sensitive to Movie Player and MUST be in uppercase. This is the reason you should use Clie File explorer as it allows you to change the extension of the mpeg and make it uppercase. No matter if the movie ends in ".mpeg" or ".mpg" you need to make it end in ".MPG"
6) Open up Clie Movie player and play
7) Of course you can just use Clie Data Import and drop mpegs from your computer into the "/DCIM/100MSDCF" directory as long as you comply with the above naming conventions.
Hope this helps