Do you mean that the icon next to the songs has changed from iTunes to WMP?
Sounds like WMP has become your default player. If you want to see the iTunes symbol, you'll have to make iTunes your default player

Go to your LW library. Click on one of your songs then click Explore. Now your saved folder's open. Right click on a song > open with > choose program. Select iTunes from the list. Tick the box to always use this program to open files of this type > ok.

That should do it