clicking sound when turns on

ive had my imac g5 for about a year and a half now and it started making a clicking sound when it would come back from sleep. a couple days ago i shut it down and now i try to turn it on and it makes the same clicking sound but osx never starts up it just shows a white screen and eventually a folder with a ? inside pops up.

i have a feeling its the hard drive and i also am past the warrentee so its prob gonna cost me a bunch to fix

http://docs.info.apple.com/article.html?artnum=58042

Try Disk Utility from the install disk. (repair disk) If it is the HDD, it should let you know.
Also, the Apple Hardware test.

i ran the hardware test and it said there was no problems. weird enough i took the disk out and restarted and everything worked.

so luckily im on it right now n im just backing up what i can to some disks n then ill prob bring it to the apple store to get checked out and ill prob spend massive amounts of money for it

Keep an eye on SMART verified in Disk Utility. If it advises failing get a new HD in there asap.