First you should open the terminal input the command free, then past the results it here.
So that we may help you.
If you prefer here are some patches not solutions:
I would recommend a full clean install. (at the bottom I have explained how to do it)
A quick patch not a solution might be installing gnome partition editor.
Then resize your partition.
The format the knew allocated space (e.g. 2gb=2048 MB) as swap area.
Here is a good video: https://www.youtube.com/watch?v=xLur2TfNVXE
Here is a tutorial how to do a clean install: http://www.ubuntu.com/download/desktop/install-ubuntu-desktop
There a good video in portuguese with a creation of swap area in youtube. It is called Instalação do Linux Ubuntu 13.10 (Dual Boot com Windows 7).
Where you should mount the ubuntu image into a usb portable hdd or cd.
Then boot from there. Normally you have boot while long pressing F12 or F2 or ESC key to choose the place where you want to boot from.
Next you will see a screen where you can cancel or continue. Click continue.
Then choose installation type as "something else".
Create 2 partiton 1 with 2gb (2048 MB) and the other with the rest of space you have left.
The 2 gb one is optional. If you create it you should change it's type to swap area.
And the first one to journalling ext4. and choose the mounting point as "/". Choose this partition to install your ubuntu.