well, yeah, if that works i dunno why not. Just rclick propertyhandler subkey, export the key as a .reg file and save it somewhere safe., then just go ahead and delete the Value. Don't like what happens? ..then simply dclick the .reg file.
[easy way to get to that key in XP is just to search for systemfileassoc]
What happens if u go into explorer > folder options > file types and change the default player to another one that you may have instead of WMP?

here the some pics of my prosses while the problems occurs!!!

http://www.redrival.com/orient/image/1.jpg

http://www.redrival.com/orient/image/2.jpg

http://www.redrival.com/orient/image/3.jpg

hope that can show sth !?

err.. i cannot get into redrival.
What happened with that reg tweak you wished to try?

wierdest thing with red rival you have to click again after you get the warning "forbiden directory...or sth" press enter on the address bar and it'll go!!

didn't try the keyreg yet!!!