You can use freeware software like ExactAudioCopy or AIMP to rip Audio CDs to MP3 and other formats (including lossless ones like FLAC).

When you use Windows Media Player to rip CDs to WMA, you should disable the usage of DRM protection in the settings on the CD Ripping tab. You may also rip Audio CDs to MP3s with WMP.

My suggestion is to re-rip your Audio CD instead of trying to get licenses for your files (Unfortunately I have no idea how to obtain licenses even if you have a receipt). As an option I can recommend to download the same album from p2p networks using software like uTorrent. Try to find audio files ripped losslessly. I only suggest it because you own the same CD, so this shouldn't be considered as piracy.