I have a dell perc controller and was able to fix this by going into the scsi controller bios/option (control M at startup) in the options I change the mode of the card from i20 mode to mass storage and this seemed to work no problem.
I can confirm that this works on the Dell that I have tried this on (a PowerEdge 2300). I will try on the 4300’s next week. Another oddity about this is that I was able to install Ubuntu server 8.04 without making any changes to the BIOS setting. However, once the machine rebooted, it did not see the megaraid controller. Perhaps the ramdisk for the default kernel loads the newer megaraid driver that does not support the older PERC2/SC card. In any case, the change in the BIOS from i20 to mass storage worked for me. If you do not see the option to switch from i20 to mass storage, you may have an out-of-date BIOS. See the instructions in the thread quoted above on how to update the BIOS.
Centos 5.1 works on the machine with no problems as well once the mass storage change is made.