I have tested the files and it works. You can check this :https://dl.dropbox.com/u/70663178/first.xml
If it is not playing in the studio then the reasons could be:
1. Some of the standard RSS formats are not read by the XML player, the format needs to be in the same way that i have put it, If you have header lines it does not display. Please check the XMLvideo tutorial example.
2.If you want to test it locally in your PC it is better you have an webserver in your PC (XAMPP is a good and easy product).