See Below

Hello,
We have a dell dimension 3000 desktop and its hard drive has begun "ticking". It is very loud (much louder than the large window fan) and about 1 tick/sec. Other than this the computer is purring like a kitten (a asthmatic kitten that just ran a marathon!)

P.S. the computer is 5 years old.

In my experience, that's a sign that it's failing. I'd back it up asap just in case it does.