I have Windows Media Player but it does not support aspx webcast. What is the best media player to use that will allow me to watch a aspx web video?
I believe we have a misconception here:
If, whatever you want to view, links to a "webcast.aspx" file then it's still a web link, not a video stream URL. It's the file extension for ASP.NET web applications. Unless this web application returns or forwards your client directly to the webcast stream URL it won't work in any (video) application.
Open the URL in your browser and see what happens. If nothing happens at all, the site stays blank, then I would assume this web application is broken or unavailable and the owner/programmer of the site has to fix it.
As Oron said an example of web video?
How to Open ASPX Files
I've not heard of "aspx webcast" or "aspx web video". Can you give an example?