If you used you, just issue the following command "rpm -qa | grep kernel" and see what comes up. Once you have a list of kernels you want to remove you can issue the "rpm -e <name>" without the brackets. I list them so I can just select the kernel name and paste is after the rpm -e command. Some kernels are close in name and numbers, so make sure you do not remove your live kernel!
"The eyes of the LORD are in every place, Watching the evil and the good." Proverbs 15:3