How do you know if your Soundcard is having issues?

Well, recently I've had Sound problems, however, they're not too bad.
It could be that I have to rotate the headset plug in the computer, else I will only hear sound on one ear? Sorry my english isn't the greatest. I've tried this on multiply headsets, they all experience the same issue, so it's not a problem with the headset.
The second issue is, earlier today my music program said "Could not play your music due to a problem with your soundcard".
That's when it hit me, how do I check this?