I have a kernel panic that doesn't respond to booting up with the shift key depressed.any suggrestions

All the boot key combinations need to be pushed immediately after you hear the boot chime.

Kernel panics are usually caused by a hardware problem – frequently RAM, a USB device or a Firewire device. What external devices do you have connected? When trying to troubleshoot problems on a laptop, disconnect all external devices. Do you experience the same problems?

To eliminate RAM being the problem, Look at this link: Testing RAM @ http://guides.macrumors.com/Testing_RAM Then download & use Memtest & Ramber.

Do you have an Apple Hardware Test disc (the AHT is on the Install/Restore DVD that came with your Mac)? Running the Apple Hardware Test in Loop Mode is an excellent troubleshooting step for finding intermittent hardware problems. It is especially useful when troubleshooting intermittent kernel panics. If Loop Mode is supported by the version of the Apple Hardware Test you are using, you run the Extended Test in Loop Mode by pressing Control-L before starting the test. Looping On should appear in the right window. Then click the Extended Test button.The test will run continuously until a problem is found. If a problem is found, the test will cease to loop, indicating the problem it found. If the test fails, be sure to write down the exact message associated with the failure.In some cases, RAM problems did not show up until nearly 40 loops, so give it a good run.

May be a solution on one of these links.

http://docs.info.apple.com/article.html?artnum=106227What's a "kernel panic"? (Mac OS X)

http://www.macmaps.com/kernelpanic.htmlMac OS X Kernel Panic FAQ

http://www.index-site.com/kernelpanic.htmlMac OS X Kernel Panic FAQ

http://www.thexlab.com/faqs/kernelpanics.htmlResolving Kernel Panics

http://www.macfixit.com/article.php?story=20060911080447777Avoiding and eliminating Kernel panics

http://macosg.com/group/viewtopic.php?t=80012-Step Program to Isolate Freezes and/or Kernel Panics

 Cheers, Tom 😉