Thanks guys, pretty much what I thought, but didn't want to run into any problems..
I would just leave it in, but since it's an old drive (~7 years) and taken its share of abuse, I'm just transferring all the important files, music, pictures and stuff to one more reliable. Then I'll format it to get rid of all the random files I don't need and have an extra drive for non-essential files I don't care about losing.