I have had the same problem. And i've tried a few things, but strangely it doesn't work perfectly for the player part. (but it DOES work)
First i opened the registry and browsed to the following key:
HKLM\Software\HTC\Biotouch\MediaHubMini\App1_3
Since that dir seems to be linked to the videoplayer on the device, you should open the dir and view the value of Path, you'll see its linked to \Windows\HTCAlbum.exe. Now...
HKLM\Software\HTC\Biotouch\MediaHubMini\App1_2 is stated to be used for viewing Photos (which exactly and ONLY seems to do that), and contains the same Path value which ALSO points to \Windows\HTCAlbum.exe.
Does that mean HTCAlbum can view both types? (i don't think so) And what happens if I change the value of Path in the HKLM\Software\HTC\Biotouch\MediaHubMini\App1_3 dir to let's say: \Windows\wmplayer.exe?
Let's try
After a softreset the Video button in the cube starts Windows Mediaplayer. It also gives me an error message stating the file cannot be played, it might be corrupt or not supported. (weird because i'm not opening ANY file)
Anyway, after manually browsing to my storagecard, i can select the right folder and play my recorded videos. Now let's see if we can fix the storage path of the camera, shall we?
I open HKLM\Software\HTC\Biotouch\MediaHubMini\App1_3\param. The value I enter is \Storage card\DCIM\100MEDIA\ Which i think is also the default path, but i could be wrong. In any case, after i do a small test by recording a video, it's saved in the \Storage card\DCIM\100MEDIA\ directory and it plays in Windows Media Player.
Now I just need to get rid of that annoying Error message when starting up WMplayer. You could also use coreplayer if you have it, i'm not so fortunate
Hope it was of any use.