IMac won't load, I've tried several things, advise please

I have a 3 year old iMac, running snow leopard and I can't get it to load past the screen saver. I made a generic white screensaver a few weeks ago, when I was having ghosting issues and have just left it on the machine. Last night i put it to sleep, this morning I saw my white screen saver, with a spinning disk. I shut it off, now I have no spinning disk on reboot, just a chime when I start it and the screen saver appears. I tried several things, holding down the S key to start in safe mode, hoping to repair it by putting in the installation disk, holding down the C when it starts, nothing works. I can briefly hear the installation disk spin and then it stops. I tried holding down option, starting it while holding down my left mouse button, I tried starting it holding down the T key, I unplugged all peripherals except the mouse and keyboard, but it's hanging on that screensaver. I do still hear the chime, but thats it, no spinning wheel, nothing. Thanks for for any help you can offer.

You can not get into Safe Mode by holding down the "S" key. Instead, try holding down the Shift key as soon as you hear the chime. If you can get into safe mode, shut off the screen saver and then try to reboot normally.

If safe mode won't work, try booting the machine with your install DVD, and run Disk Utility verify and repair.