I do not know if this belongs in the beginner section, but since this is my first use of the forum, that is where I assumed it would go

A while back I purchased a Dell Inspirion with Windows 7 installed. I found a site which walked me through setting up dual operating systems and added Ubuntu 12.04. I almost never use Windows. I wanted it only for using the National Geographic map program.

Everything seems to have worked Ok, but a day or two ago I got a message indicating the boot partition was nearly full. I ran Gparted and found the boot partition was over 90% full. However, I do not know if it was 90% full when I set up the dual system. I do not know if updates add to the boot partition.

Also when the dual system was set up the booting wound up being done with the Windows boot loader. In addition I am no longer able to gain access to BIOS by pressing F2 or F12

Since I use the map program infrequently I want to simplify my computer by having it run only Ubuntu 12.04 so I'd like to use DBAN and then reload 12.04, but I do not know how to do this.

When I restart the computer I can hear the CD drive spin first so I'm fairly certain it will boot first from a CD. Does this also mean it will boot from a stick in a USB? Assuming a successful DBAN wipe, will 12.04 automatically partition itself?

I cannot operate from the terminal. I only use the GUI.

Thanks for any advice.