Hi Donnier. You say you hate ubuntu because slowed down your computer and therefore you would prefer install LinuxMint with MATE graphical interface. You also mentined that another person did the actual installation.
So I have a question and a suggestion for you.
The question is do you have full administrative rights to the computer? are you able to install, remove and edit applications in the computer? If you can edit and install applications in your computer here is my suggestion.
Why no install MATE in Ubuntu? I am guessing the reason why your computer slowed down is because the default graphical interface in Ubuntu uses a good amount of resources in your computer. You didnt mention the model and maker of your computer but the Graphical interface is makin your applications take longer to load.
So if you install mate perhaps that will speed up a little more and perhaps improve perfomance.
Here are the steps to install MATE in your computer
Open up a terminal and type
sudo add-apt-repository "deb http://packages.mate-desktop.org/repo/ubuntu precise main"
type your password when prompted and hit enter the program will ask you if you want to proceed hit enter to confirm if you are asked
then once is done running type
sudo apt-get update
type your password if asked and hit enter, let it run until is done
sudo apt-get install mate-archive-keyring mate-core mate-desktop-environment gdebi
and type your password if asked, again let it run until is done
log out of your computer and log back in but at the login screen click on the round bottom next to your user name (See attached picture) and selec mate there then proceed with your session.
Good luck to you