Clicking Hard Drive

Hope someone can help me out on this one. A few weeks ago my hard-drive started making alot of "click-clacking" noise (like it was trying to access the info it was after)and since then it does it alot!!. I have ran scan disk and de-fragged it 3 times in the last couple days (fragmentation was less than 3-5% the last time) If I dont do anything,all is quiet but when I run programs or especially when I'm on-line "surfing" or playing games, it sounds like a little train down there! (clickity-clack) I'm running Windows Me, the hard drive is 30 GB and only about a third full. Since its the worst when I surf ( I usually use Opera or Netscape-hate IE) I even tried emptying the cache to see if maybe it was full and the noise was it dumping info but didnt help. It had this noise about 6-8 months ago and cant remember what I did to cure it but I did get it to stop back then. Would appreciate any ideas on this-Thanks

 

It's about to die, and render your data irretrievable. Back up anything important ASAP.