ENFILE Error

Red Hat 7.0 i386. NR_FILE in fs.h = 4096. Using the bash ulimit command I've set the max open files per process at 5120 temporarily and I am getting the ENFILE error. Is there any way to up the NR_FILE value without re-building the Kernel? If not how difficult is it to rebuild the Kernel on RH7? Any suggested doc? Thanks.

read http://www.linuxdoc.org/HOWTO/Kernel-HOWTO.html