Switch iTunes and WMAs from Windows to Mac
Source from www.makeuseof.com by Jackson Chung
Switching over from Windows to Mac is relatively painless because Mac has support for a lot of commonly used files like Microsoft Word documents, Powerpoint slideshows and Adobe PDF files. So, compatibility is hardly an issue. One thing which you do have to take note of however while switching over to Mac is your iTunes library.
iTunes for Windows is built with Windows Media Audio (WMA) support – it is able to play and convert WMAs. However, because WMA is a proprietary codec, it isn’t available in iTunes for Mac. If you’re not careful, you’ll be left with a lot of WMAs which will be unplayable on your Mac.
Before we start, I would like to mention that this tutorial was written under the assumption that you are running the latest version of iTunes ( iTunes 8 ) on both your Windows and Mac. Please update before proceeding to avoid any complications which may arise.
The easiest way to dodge this problem is to convert all the WMAs you have while you’re still on your Windows machine. In your iTunes General preferences, under ‘Import settings’, make sure to have AAC or MP3 selected. Configure the bit rate if you like but because you will be converting from one lossy codec to another, there’s bound to be a profound loss in quality.

While you’re still in Preferences, go over to ‘Advanced settings’ and check “Keep iTunes Music folder organized”.

Now you’re ready to convert all of your WMAs into the codec you’ve just selected. To do this, control-select your WMAs, right-click on one and choose “Convert Selection to xxx” (Where xxx is either AAC or MP3). After the conversion is complete, you may choose to delete the WMA copies if you like. Then, consolidate your library from the ‘File>Library’ menu. This will ensure that all the songs in your library are copied and organized into the iTunes Music folder. Normally, it’s located in “My Documents/Music”.

Now, you’re ready to bring that iTunes Music folder over to your Mac. Place it on your Mac desktop.
If you haven’t already, run iTunes on your Mac for the first time. You’ll be prompted with the initial welcome setup procedure. When it asks to search your drive for music files, make sure to decline. At the end, you’ll be presented with a fresh, empty iTunes library. Now, quit iTunes. By default, it would have already set up its own iTunes Music folder located in ~/Music. Go over to this location and delete the iTunes folder then copy and paste your iTunes Music folder from the desktop into it (the one which you have just brought over from your Windows computer). After all this is done, launch iTunes and you’ll be rewarded with your old, personalized iTunes library.
Another method of dealing with the whole WMA malarky is to get an audio converter. The first one which comes to mind is EasyWMA which isn’t free but very popular. A little hidden gem is Switch for Mac. It is capable of converting WMA to many other audio formats compatible with iTunes.

Switch is also available for Windows so you’ll have the convenience of converting your songs before making the switch over to Mac, if you prefer.
And here, I would also recommend using TuneClone Audio Converter, which can be used to either convert M4P(protected AAC), M4B and M4A music songs to MP3, WAV, unprotected WMA or convert both protected and unprotected WMAs to MP3. Not free, but well worth a shot if you have lots of WMAs ready to be switched to Mac.