G4 mini won't start up!

I have a PPC Mac mini (specs in my sig), and it won't start up. Here's what it does: It shows the grey apple on the grey background, it goes into the logon screen (or whatever you call that thing where it says Mac OS X is starting up - the one with the window with the huge apple logo in silver), then it loads the bar until it's full and stays there. the mouse pointer works, the bar is in motion, and the computer is silent. Just that little hum.

I'm freaking out. All my stuff is on there please help

Update: It does chime, it shows the grey apple plus spinning thing, and then the blue screen and that window where it says mac os x starting up (words may differ, I'm translating this off the top of my head), and it loads and stuff and then it stops.
I tried booting the CD, ran the disk utility, repaired it. It concluded that minor repairs had to be made on the boot header or some other header and another thing. That didn't change anything.
Safe mode doesn't work, it doesn't get past the grey screen.

Can I somehow reinstall Mac OS X but keep ALL my files without an external HD (i don't own one and don't know anybody who does)?

Mernak said:

Sure, just check "Archive and install" on the options menu (a little button on the bottom left of the installer window) when you are reinstalling the OS. It saves everything, just overwrites the system files.

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It worked, thanks! I put the CD in, set the options, started the install and went away. I came back after a half hour to check the progress, and I was already greeted by the matrix screensaver i had all along. Windows has really made me bitterly realistic. I guess I'll have to get used to not going into terror once my computer doesn't work

blodwyn said:

Good news, now how about setting up a regular backup and avoid even mild terror

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I am doing that, but after this, I will do it more regularly (that is, more often). I hope to be getting a big LaCie for Xmas, guess what I'll use that for