Why is CD-rom drive acting weird?

Okay, I just recently had a new hard drive installed on my computer. Everything has been cleared out and I've basically had to start from scratch. There was no audio, no DVD decoder etc. I installed audio, installed a DVD decoder so now I can watch movies. However, something is wrong with my CD-rom drive. It can play my burned CDs (I don't have a regular CD to put into it yet to see what it does with it), but all of the files on there are .cda when I clearly burned them in .mp3. Also, when I try to burn CDs it burns everything correctly and then ejects the CD saying that it's complete, but when I put it back in to play it, it reads it as a blank disc. HELP!