help! my mac keeps turning off before the loggin screen:O

i was on my Mac g4 last night just browsing the internet and chattin on msn when all of a sudden everything froze! unable to do anything hit the reset button, the sound sounded and the white loading screen with the spinny thing and apple logo came up and stayed for ever. i reset aagain the same thing happend. i tryed turning it all the way off and back on, same thing however after a couple of attempts my mac would turn off at the white loading screen!:O

can anybody tell me why is this happening and how can i fix it please?!

it would be MUCH appreciated as i need to do my university work.

Have a look at out OS X troubleshooting guide:

http://www.mac-forums.com/forums/showthread.php?t=93819

Start at step 6 and work your way down. Let us know if you need any additional help.

bad

When mine started to do that i took it to the apple store. my harddrive had crashed,