I believe you are correct in that the new hardware has a different hard drive controller than that in the old hardware. (The Dell site may confirm this.) The controller you are interested in is the one that controls the drive that has the root partition on it. The problem you are experiencing is almost undoubtedly that the driver for the new controller is not in the initrd file (initial ramdisk -- normally found in /boot/initrd...). The initrd gets mounted first thing after grub finishes. Its job is to find and mount the root partition, then hand off control to it. It does no test to see if this was successful -- it does its job blindly. If it has no driver for the controller, then it will be unable to do its job, leaving you with a kernel panic.
Fixing this can be done, but it is not trivial, and I cannot give you step-by-step instructions as I've only done this 2-3 times. It involves booting using another media, like your installation disc, and entering a rescue mode. Then you mount your hardware's partitions under a single folder (like /mnt) to recreate under it the filesystem that your hardware normally has (e.g. /mnt/bin, /mnt/usr, /mnt/usr/bin, etc.) Note that this may require manually loading a driver for your HD controller, but this is somewhat unlikely. If manual driver loading is required, you'll need to figure out which driver to use, such as by searching the web. Also, you may need to create device files under /mnt/etc. There is probably a simple way to do this, but I have yet to discover one.
Once your real filesystem is recreated, then you'd need to "pivot" your root. That is, what you've created under /mnt will be pivoted to become / (and what was / can be pivoted somewhere, like the post-pivot /mnt, but I don't think this is necessary). If you get to this point, you are 90% done. You could probably run kudzu at this point (you may want to make backup copies of /boot/initrd* and /boot/vmlinu[zx]*). You may also be able to get copies of your distribution's latest kernel RPMs and just use them to "upgrade" your kernel (you may need to force the installation -- rpm -Uvh --force ...). This ought to recreate your initrd for the new hardware. If this works, you're probably all set to shutdown and reboot.
Before trying this, search the web for kernel panic and rebuilding initrd. It'd be nice to have another PC available so you can refer to the web as you are going along. Good luck. If you try this, you will learn a lot of good stuff.
Last edited by bwayson; 07-09-2009 at 03:50 PM.