|"Do ou think my music on my pc is a mixture of mp3 and wma"?|
we have absolutly no way of knowing that. That is something you can determine by the file's extention.
Your player is capable of playing both so that shouldn't be an issue. I would suggest at this point you re-format it as per the instructions, then just add a few songs at a time. It's possible you added too many at once and ran out of room and possibly corrupted the data in doing so. After adding the first few songs, have a listen and see if they play ok.