Ok, so recently my computer has been making a strange clicking noise. A good amount of clicks and stops for an hour or so and then starts up again. Now, I've heard that clicking on a computer is really bad. I'm unsure where it's coming from exactly. But I think that usually means a hard drive thing. I haven't made any changes to my computer, but I'm still a little worried.
I know it's probably stupid to worry, but I have some important shit.
Should I start backing everything up now before something bad happens?

EDIT: Not too long ago, it started clicking and everything locked up. I restarted and I got a disk read error. Holy shit.
I shut down and waited a bit then tried again. Cannot read system OS or something. I waited longer and finally the computer starts to work again. I know for a fact that this machine is fucked up, now.
What is the best way to back up data? I can't burn CDs because the CD burner went out one day. I'm thinking of uploading just the important shit to megaupload or something so I can download it on a new machine.

This thing probably doesn't have much time left...

Depends on how much stuff you have to back up. If you only got a couple of gigs, just get a memory stick if you don't have one. If you got much more, get an external HDD. If you don't got almost anything at all, then uploading is fine too I guess.

I agree that it is most likely your hard drive beginning to fail and that backing up would be smart!  That said also run the comp with the case open and double check that there aren't any wires getting nicked by the fans.