macbook pro battery won't hold charge

I replaced my battery a while back. The cycle count is only 20. Anyways, I was still having problems and I discovered that I needed to replace the hard drive on my macbook pro (it's mid-2010 and was a used buy so it wasn't really a surprise and the warranty was nonexistent). Well, I don't know if the hard drive dying was somehow slowly murdering my battery but the charge capacity quickly plummeted. Now, I've replaced the hard drive and the battery still only holds a charge for, like, barely an hour, if that.

Do I need to just replace the battery again? I reset the SMC (or whatever it's called) and I'm still having the same problem. Is there something else I can do to fix it or did the death of the hard drive over work the battery into permanent damnation? (When I first got the battery it held like 5 hours or whatever. I don't remember.) Or is there something else I need to replace?