I used my kernel name from 'uname -r', a command I got off another post on this forum. Mine was 2.4.21-4.EL.
Look in /lib/modules/ and there should be a directory with your kernel source in it, named after said kernel source. If not, get the kernel source installed (I used Red Hat 9, so there was a kernel source RPM for this - you may want to ask the forum about how to do this if you are using some other version).
I got the kernel name thing from another post as well. You may want to search around a bit, as I have lost the link.
Hope that helps.