Need help with partitioning

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http://askubuntu.com – I bought a new laptop with no OS and decided to try to Linux (Ubuntu) for the first time in my life. It was a clean install, my laptop had no other OS present in it, not even DOS. While installing, it asked for partitioning. Out of the 320GB of free space I created a new partition of 20 GB and installed Ubuntu in it. The rest of the 300GB is still available as free space. Soon I realized that I can't use the 300GB of space and that only 20GB is available to me for use. Can anyone tell me how I can take away some free space away from the 300GB and add that to my 20GB partition? I have insta (HowTos)