I've been using the dual boot system with ubuntu 12.04 LTS and Windows Vista. I no longer want to use Windows but wish to keep all files. How do I make Ubuntu be the sole OS without wiping out everything I've done.
If all you want is to bypass Vista at power up and go directly to Ubuntu without seeing that menu to select OS, you can easily do it by editing /etc/default/grub file.
Set the GRUB_TIMEOUT to 0 to skip the menu at startup. Optionally you may also want to set GRUB_DEFAULT to your desired entry in the GRUB menu if its not already set.