According to Jim Recap: The Tale of the Tape (Part 2)
In The Tale of the Tape (Part 1), Jim believed that Cheryl had made him a mix tape, and they had shared many special moments in their lives together to the tunes on that tape. But after pulling the tape out of hiding in order to use it to get himself out of the doghouse, Jim needed to get it put on CD, since they no longer had a tape player.
In doing so, they boosted all the levels, and this exposed a hidden track that said "I love you Cheryl", which in turn exposed Cheryl's secret - she didn't make the tape - her ex-boyfriend Chad did. Jim just assumed it was for him. Cheryl destroyed the CD in the blender while making Jim a smoothie (no telling how that could have happened), hoping that Jim will never hear the new track.
When she tells Jim about it, however, he tells her not to worry - it costs as much to make one CD as it does to make fifty - so he made fifty (and sold one to Andy to cover the cost of making all of them).
Then he plays the CD, he hears the new track and he finds out what Cheryl has been trying to hide from him all along - and that's also when he also finds out that she was getting ready to break up with him when he found the tape in the first place.
But when she heard the emotion in Jim's voice when he started talking about all the music, she knew that there was more to him than just the big lunkhead, and that was the turning point in their relationship, no matter who made the tape.
Still, Jim has a tough time getting over things, and it's hard for him to imagine that the tape that they've had for so long is now gone. So he needs something else to hold on to, and Cheryl tells him to imagine the purple sweater that she was wearing that night, which does just fine. Unfortunately, Chad gave her the sweater too, but Cheryl says her mom did, and the problem is solved.
No word on what happens to all of the other CDs.
Cheryl's cat Mr. Feeney also makes a brief appearance in her apartment in this episode.
