Yea, you need QT Pro. The plug-in allows you to open WMVs in Quicktime and play them. To convert it, you need QT Pro's 'save' or 'export feature'. The plug-in is $9.99 and QT-Pro is $29.99. All their products require OT-Pro. I have their Studio Pro version.
How many do you need to convert? If it isn't more than a few, send me a copy in an e-mail and I'll convert them over to MOV format for you.