Sendkeys problem with Vista

I am pretty sure that this is a problem with Vista and not I.E. but I have
bni idea where in the Vista forums to post this. The following code works in
XP with IE 6 and IE 7:

function playFile(player, file)
{
var WshShell = new ActiveXObject("WScript.Shell");
if (WshShell.AppActivate("Windows Media Player")) {
WshShell.SendKeys('%FO');
WshShell.SendKeys(file);
WshShell.SendKeys('{ENTER}');
} else {
WshShell.Run('"'+player+'" "'+file+'"');
}
}

It is called by passing in the fully specified (C:\...) location of the
WIndows Media Player and an mp3 file that I want it to play. When the Media
Player isn't running, it is started and the file plays. If the Media Player
is running, it can't open the file. After some examination, the File Open
Dialog box is dropping the first characters of the file name (as in the C)
and
of course, WMP can't open ":/...". ANy Ideas?

I am actually using another program that doesn't work by associating a file
type. It always starts a new instance of the program. I tried it with WMP
to see if the issue was with the program I use and it fails the same way.