Ah Vista! Sorry, I somehow missed that part. I see what the problem is now, as that key no longer exists under Vista. The problem exists in the core.js file in the section that determines the %CDROM% variable (lines 87 - 91): if (cddrv=="") { cddrv = WshShell.RegRead("HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\Setup\\SourcePath") + "\\"; cddrv = cddrv.substr(0,3); } The If statement should be changed to this to accommodate Vista: if (cddrv=="" && getOSver()!="Vista") @Kel This is really not a good way to be determining the CD-Rom drive letter as the SourcePath value can be a CD-Rom drive, a network drive, a UNC path or an external drive that is no longer connected. I know you probably didn't write it, but I would suggest removing it all together.