iMac G3 Snow 700mhz Click noise

I just recently got an incredible deal on a rare 700Mhz Snow iMac G3. I got it from a lady who thought it was dead because the hard drive finally died. Anyway, I installed a hard drive I had laying around the house in the machine and installed Tiger on it. Everything works great except when the machine goes to sleep the hard drive makes a click noise over and over until I wake it up? Has anyone else ever had this kind of issue?