itunes import mp3 folder

By adding my MP3 files in iTunes, why not itunes makes?
I just upgraded to Windows 7 and started fresh with itunes. When you click "Add folder" in iTunes to import "my music" folder, put all the songs in iTunes, but only to listen to them. I can not put on my ipod, and still are in mp3 format. Why can not iTunes convert them as it always did before?
Because iTunes can be played mp3 files only converts WMA files.
Otaku Approved: Tutorials – Putting Songs on your DSi
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