How do you force a video to open with a diff app in 2.2 ?

[Guest mistermentality]

I am using 2.2 rom and when I try opening a video file streamed from the net it always uses the built in one. I tried setting MixZing as default by opening a video file of the same type on my sd card and choosing to always open future video files with that app but it doesn't affect the playback of internet video files and so many result in a "cannot play video" message.

As far as I can tell "Music" is set to be default player but neither it nor any app in the settings menu for applications has any evidence of being the default so can anyone advise me how to force a different app for internet videos please?

Thanks.

Dave