wma files that play but won't convert

I have a bunch of wma files that are ok when I play them with Winamp or media player, but won't convert to mp3. I tried programs from various vendors but they give me error message and crash. I suppose it's a codec issue? I have windows media player 9 codec pack installed. Is there any way to resolve this?

 

Did you obtain the WMA files from an online music store?

 

I recently purchased some wma music files from walmart.com (received a free gift card)but they are useless to me unless I can put them on my ipod. Is there a way to convert these files and use them with iTunes?? Help!? What a BITE...!

Thanks

 

import cd ,using imtoo cd riper,it can convert AAC to MP3