Windows Media Player is the most common MP3 player on Windows computers (and chances are your PC computer already has a copy installed). Here is a step-by-step for playing the MP3 CDs in your computer with the program 'Windows Media Player' on your PC computer:

1. Insert the MP3 CD into your CDROM drive in your computer
2. Go to the lower left of your screen and choose: START MENU>PROGRAMS>WINDOWS MEDIA PLAYER
3. Once Windows Media Player is open choose the menu: FILE > OPEN (or Control-O)
4. Navigate to your CD drive (which is most likely in your D: drive) - to do this you may have to go to the Desktop: My Computer: D:
5. You should now see the contents of the MP3 - it may be just a single folder -- if so, open the folder and then inside the folder there should be a long list of .MP3 files
6. Click on any MP3 file and click OPEN
7. The file should then start playing (just make sure your speakers are turned up) and you're set!