Infinite Spinning Startup Circle. Grr.



I have owned my iMac G5 for a little over a year now, and never had one little problem with it.

However, after I installed the automatic updates (itunes 7.7, and a few other system updates) and restarted the computer, i found it would never get back to the login screen.

I tried reading some other guides, like unplugging all peripherals..but to no avail.

It makes the "Bing" startup noise, and the little circle spins.. and spins.. for hours..

I'm at a loss of what to do.
Sorry if this has been posted somewhere and fixed in the past I'm just a little sleepy and kind of upset over it.

Thanks for any help in advance, I'll check back later. <3