[CentOS] Getting kernel source for 2.6.9-42.ELsmp

Hello!

I need to get an arcnet device driver up and running. Normally it appears to be distributed with linux, but not installed. So, I need to compile and install it, naturally. So, where is the kernel souce for 2.6.9-42.ELsmp? I can find kernel source for 2.6.9. BTW, I obtained 2.6.9 and tried compiling it, but all I got was *.o files and

insmod: error inserting 'arcnet.o`: -1 Invalid module format

Seems that the rest of the /lib/modules/2.6.9-42.ELsmp/kernel/drivers/net appear to be *.ko files.

Hope y'all can help! Charles Campbell

P.S. sorry if this is a duplicate; my first copy went out over an hour ago and I didn't see it show up