Sounds like you upgraded your kernel twice (new kernels appear as dependencies of linux-generic whenever they're released), and the grub auto-configurer doesn't remove kernels from the list, it adds them. So if you keep installing more and more kernels, it can eventually get out of hand.
There's a couple of things you can do:
Option 1: Don't update any of the kernel packages
The simplest option. Does just what it says on the tin. Simply put, during an update don't update linux-(anything). You can also use the following to keep it from installing new versions of the kernel echo [package] hold | dpkg --set-selections, replacing [package] with each linux- package you have.
Option 2: Remove linux-generic
This is potentially dangerous with apt's dependency resolving, and I wouldn't recommend it but you CAN remove the linux-generic package along with all the linux-[something]-generic packages you have that don't list a version number. They're just meta-packages. Be careful though - it may try and remove the kernel itself which is Really Bad.
Option 3: Run apt-get autoremove
Do NOT use this in combination with option 2, because it will DEFINITELY try to remove your kernel. However, if you take my advice and don't use option 2, this should be fine since it removes any packages which no longer meet dependencies and were not deliberately installed by you. In other words, it'll clean up all the older kernels you have lying around leaving only the latest one.
Whatever you choose to do, you should definitely edit /boot/grub/menu.lst as suggested by RiCtee and delete the un-needed bootup options.
Just edit /etc/grub.conf
You could also remove the kernels you don't want from /boot
Go into synaptic. and search "linux-image". select all installed ones but the latest. It maybe linux-image-2.6.X-Y. and the press apply. (Installed packages' checkboxes are gray)
Ok, I'll try that.
What strikes me as odd is that Vista gets listed twice as well :S And it's been that way since I installed Ubuntu...
sudo gedit /boot/grub/menu.lst. Got it.