The whole world will know now that I am not the brightest bulb - OS wise anyway. I was having problems with Ubuntu 12.04 so thought I would re-install it. After it began, I realized I really did not want this and couldn't stop it. It installed a 2nd OS with the same name in another partition. How do I delete that new OS?
If GRUB the boot-loader gets messed up and the computer does not boot to Ubuntu, follow the second option described at Boot-Repair to fix reinstall GRUB. Also see this detailed instruction for installing GRUB from the Live CD/USB.
Hope this helps
Did your new install also overwrite GRUB? In that case, restore GRUB from the desired installation by following:
After that, use a disk-management tool like 'Disks' to format the left-over partitions and put them to better use.
p.s. if that was the stupidest thing mankind has ever done, we'd be living in a better world now :)