I"m no computer expert, but here's what I did.
Pay attention.
Go to start menu and then into programs directory. Click onto Msdos prompt. And then from there, go to the proper directory, for instance, if you have the file saved to the desktop, type cd windows/desktop. My ms dos begins in the directory of windows so I just type cd desktop. I locate the file and rename it. For convenience I rename the opeth video file beforehand to "1" via the right button on the mouse, sicne it's easier to deal with.
Anyway, here I type "rename 1.zip 1.asf" (or whatever the name of the file is for you)
Then I go back to desktop and rename the new file whatever I want- which naturally would be "opeth drapery falls live"
There's got to be a better way to do this. Too bad the simpel "rename" doesn't actually change file extensions- but then again maybe it does, and I have just not learned how to activate that......