I wanted to use the enhaced Centos 4 krenel I was reading the readme.txt at Readme.txt . I found the config files at Kernel config. I couldn't locate any docs on hoe-to do it so can i run this method up the flagpole and if you know where it is wrong could you please help.

copy config file to /usr/src
then cd /usr/src
make meuconfig

choose to load an alternative config file and then

make && maje modules install

wait for this to complete and reboot.

Bonus question is there any way to keep the default kernel in available but boot the new kernel by default?

I can really only answer part of your question, because I don't use CentOS (RH?). The kernel does not reside (run) in /usr/src, only the source code. Running make && make modules_install will only compile the kernel, but will not install it, unless CentOS does some magic and teleports the kernel image to /boot You will have to manually copy the kernel image to the /boot partition and adjust your /boot/grub/grub.conf. At least that is how it is done in my distro, but as I said, I am not familiar with CentOS.

It is entirely possible to have several kernels installed and choose from one - I am doing that as we speak. Again, my caveat - don't know didley about CentOS.