WMP uses an outdated MP3 encoder, hence 320 from WMP is of lesser quality than the likes of LAME for example. Of course they may have caught up now but when I used to use WMP it was poor.
As always I'll recommend Exact Audio Copy, free software and with a bit of tweaking can rip better than any other software I've come across, it locks the drive then verifies the rip, you can then convert to any format you like (MP3, AAC, FLAC, etc). I've had issues with certain CDs ripping and overlapping each other where as EAC is perfect every time.