I like my co-worker.

You mean to give it to him just because it's something he seemed interested in? Sure. He might even notice you more, but don't push it.

You don't know he doesn't like you, by the way. It is almost impossible to like someone for very long if you know they actually dislike you.

Relax. Try to get things in perspective. It's a CD - not a wedding ring!!

Relax. He can't see your heart beating so fast. Just try to get to know him better.

Don't act. If you can't think of anything witty to say, or do, that's okay.

But there are LOTS of signals that girls can give off that are otherwise harmless : playing with hair, tossing your hair, palms outwards, turning your full body towards him, holding eye contact a moment longer than normal, looking up at him without tilting your head up (starting from appropriate position of course), holding your lips slightly open, slow smiles when you see him, pushing your breasts together with your shoulder (appropriate timing of course), leaning in towards him, talking with a friend about when when you're sure he's going to see you two talking and looking over at him / then smiling/laughing/similar/& looking away...LOTS of stuff more.

And yeah, if it's a CD of music he likes, go for it. If he doesn't like you, let him know something like "I think we got off on the wrong foot, so I made a little gift for you that I hope you'll like, by way of saying 'I'd like to start this over again'...or something like that.