You only need one kernel image and one initial RAM disk compressed file to be able to boot. (The both, of course, should be for the same kernel, although that's not an absolute requirement.)
Boot into you system, start a terminal window, and do a sudo ls -l /boot
to see what's there, and then a sudo rm <actual name>
to delete the stuff you don't need. (Substitute the actual name(s) of the file(s) to be deleted.)
Generally, any sub-directories of /boot contain information needed for the boot manager, and should not be altered.
Note that your /dev/sda1
is only 228Mb in size, so you don't have much room with which to play. (You might want to use a Live CD rescue disk to resize your partitions, expanding sda1
to a more reasonable size, and shrinking the others.)
Warning: From your /etc/fstab listing, it seems likely that your root filesystem is in a LVM virtual file system. If this is the case, resizing your other partition(s) is fairly complicated, and not to be undertaken without a complete, tested, current, offline back up.
Oh, Ubuntu often stores "backup" copies of the most recent kernel and the initial RAM filesystem in the root directory.