An error like the one below will appear when you have not installed a kernel-devel package that matches your running kernel.
[root@ws-test aoe6-70]# make Error: /lib/modules/2.6.25-14.fc9.i686/build sources are not configured. make: *** [prep] Error 1
You can see the kernel-related packages that are installed with the command, "rpm -qa | grep kernel-". The version of "kernel" and "kernel-devel" should match. If they do not, the easiest thing to do is to upgrade both of them. You can "yum upgrade" to install the latest versions of all installed packages on the system, including the relevant ones, or you can "yum install kernel kernel-devel" to specify the relevant ones.
Don't forget to reboot afterwards if you upgrade the kernel.