iMac G5 Kernel Panic

I need help resolving a kernel panic error message. My computer is a 2004 iMac G5, 20" screen. To the best of my knowledge, the last known OS update was to 10.5.? Leopard (although I am not 100% sure).

Anyways, whats happening is every time I start up the computer, I hear the beep, followed by the blank blue start up screen, along with the apple icon and the loading wheel. Then, before the computer starts to boot itself, a light gray/dark gray checkerboard screen cascades down and the kernel panic message appears. I have restarted the computer tens of times, each time with the same result. I have tried safe mode options, booting from the disk (which is usually not noticed by the computer before KP shows up), and I have tried to log the boot process to see if I notice any blaring clues. The computer is old, so obviously there is no warranty left on it. The computer was a family computer and stored a lot of personal data on it, so I would like to be able to restore it, if at all possible. One thing that I have thought of is a possible error with the graphics card because of the screen change, however, I would like to avoid buying a new graphics card to find out that its not the case. Any help or suggestions you guys could give me would be very much appreciated.

Thanks,
Mike

The update 10.5.? is 8

Restart your Mac with a Safe Boot and see if the kernel panic happens again

In most cases, kernel panics are not caused by an issue with your Mac. They are most likely caused by an issue external to your Mac. If the kernel panic doesn't happen again within a few weeks, you don't need to troubleshoot further.

Depending on the model of Mac you have, restart one of these ways:
Press and hold the Power button for several seconds to turn off your Mac. Then, press the Power button to startup your Mac.
If you have a Restart button, press it.
As soon as your Mac starts up, hold down the Shift key to start up with a Safe Boot into Safe Mode. Note: If you are using a third-party external keyboard and cannot start with a Safe Boot, try using an Apple keyboard instead.
If your Mac has a kernel panic starting up, or while in Safe Mode, jump to the "Troubleshooting a recurring kernel panic" section of this article.
If your Mac starts up without a kernel panic after a Safe Boot, restart your Mac by choosing Apple Menu > Restart…, then let it start up normally. Run Software Update and install all available updates until Software Update reports "Your software is up to date". Mac OS X updates improve the tolerance for external issues such as malformed network packets. For most kernel panics, this is all you have to do.
Important: If your Mac has another kernel panic within a few weeks, continue with this article to diagnose the cause of the intermittent, recurring kernel panic.

Note: It is possible, although very unlikely, that something on your network is sending your Mac malformed network packets which could cause recurring kernel panics. If the hardware and software on your Mac checks out as OK, check the devices on your network. Make sure your router's firmware is up-to-date, and that the router is not malfunctioning. Refer to your router's manufacturer for service and support.

Diagnosing a recurring kernel panic can be difficult. If you would like to avoid this process, or do not know how to perform any of the following steps, consider bringing your Mac to a Genius at an Apple Store or an Apple Authorized Service Provider for assistance. Be sure to ask that, if the hard disk needs reformatting or replacing, they contact you about escalating your case to a special data recovery service. If you plan to visit an Apple Retail store, make a reservation at the Genius Bar using http://www.apple.com/retail/geniusbar/ (available in some countries only).