I often used UBUNTU Live booted from a flash drive to run GPARTED. Then I could easily delete old partions, create new ones, formate drives, etc. To find it, I'd just click the first icon in the list and type GPAR... by the time I got that far I would see the icon for the program.
I just finished doing a full installation of UBUNTU on an old recycled AMD 64x2 system. I used that very same flash drive. Later I ended up putting a 2nd hard drive in, and figured I'd just run GPARTED to wipe it clean. But the full version doesn't seem to have GPARTED.
Why would GPARTED be included on the live CD iso, but not on the fully installed version ???
You can install GPARTED from the repositories if you wish.
GPARTED is better used on a live disk, though, as making changes into a mounted partition can create complications. That is why its available on the live CD and you have to re-install it on the installed OS. As a different solution you can use the "disks" application to manipulate unmounted drives/partitions.