Manage the kernel images installed but not used by the user

The system must be able to manage the installed kernel images and remind the user to delete the unused images from the disk.

The best way to do this?
- the upgrade manager suggests the installation of a new kernel image
- the user accepts and then reboots the system
- after reboot, if non problems are detected, the system suggests the user to delete the old unused image: "Would you like to remove the old kernel images from the HD? Now you are using Kernel (official Ubuntu) image ver. 2.6.20-20 and the following images are obsolete but installed on the system without being used from at least 12 days: 2.6.20-15, 2.6.20-17 and 2.6.20-19! Press the YES button to remove the old images (300mb will be removed from disk)."