I had windows XP running on my computer. Then I installed Ubuntu from under windows. Then I decided I wanted to have only Ubuntu

also because I got a system message that I am out of disk space. I loaded up my system from a live Ubuntu DVD and deleted the partition with windows on it and also the other partition that had my data on it. I expanded the partition which I thought to be the system partition (since there was no other partition left It had ext format.

After that Ubuntu was working fine and I thought I have enough disk space, since my harddrive is an 80 GB ATA Maxtor. I left a small partition as backup. But after downloading a small amount of files I got the message again, that I am running out of disk space. I don't now. How can UI make my disk space bigger? I am not used to Ubuntu's file system, and I don't have the overview on how I can actually see how much space there is left for me to use. I have basically now 1 partition with the system on it and one small backup (as far as I understand). My system is (from system utility)

Ubuntu 12.04 LS
3,9 GB
Intel Core 2 2,4 Ghz
80 GB ATA Maxtor

Here are the results for sudo fdisk -l

Disk /dev/sda: 80.0 GB, 79998918144 bytes<br>
255 heads, 63 sectors/track, 9725 cylinders, total 156247887 sectors<br>
Units = sectors of 1 * 512 = 512 bytes<br>
Sector size (logical/physical): 512 bytes / 512 bytes<br>
I/O size (minimum/optimal): 512 bytes / 512 bytes<br>
Disk identifier: 0x41ab2316<br>

   Device Boot      Start         End      Blocks   Id  System<br>
/dev/sda1   *          63   123750399    61875168+   7  HPFS/NTFS/exFAT<br>
/dev/sda2       123750400   156246015    16247808    7  HPFS/NTFS/exFAT<br>