I have only had my Thunderbolt for a few weeks. I use Gmail as my primary email program. I recently received an email message with two videos attached. One was a WMV and the other was an MPG. When I clicked on PreView, in Gmail, to play the MPG video, I saw a blue bar and the text reading Loading and then I received an error message "Sorry, this type of document is not supported for viewing". I was advised to install ArcMedia. I can download and play an MPG movie with ArcMedia, on the Thunderbolt. There is no option to Download an Attachment, in Gmail, on the Thunderbolt. There is just PreView.
I do not know how to make ArcViewer the default Media Player. When I installed VitalPlayer Neon, and clicked on PreView to play the attached MPG file, it just kept flashing between Portrait and Landscape and did not play anything.