At first I installed Ubuntu 10.04 and ROS Electric following the "advice" of the distributor. Later I installed Ubuntu 12.04 LTS and ROS Fuerte using the Windows Installer from their website. It seems to be a wrong way. Now, when I start the computer, I see a first grub window for choosing either Windows 7 or Ubuntu 10.04; say I select Windows; then a second grub window appears asking me to choose either Windows 7 or Ubuntu 12.04; say I select Ubuntu; then a THIRD grub window appears asking me to choose either Ubuntu 10.04 or 12.04. It is really annoying. The problem is, in grub customizer, I can only see 10.04 when the computer is in 10.04, or see 12.04 when in 12.04. This means, the computer has multiple grub. Does anyone know how to clean up this mess?