You should be able to use a liveCD or flash in live mode and load gparted. You usually have to click on swap and right click swap-off to unmount it as liveCD's use swap to speed things up a bit. Then edit / (root).
GParted partitioning software - Full tutorial
Screenshots of using gparted
I cannot give specific instructions on BIOS as each vendor's is different. I had to take camera shots of mine as it reset everything back to defaults when I upgraded it and it took awhile to get the settings back that I wanted. Now I have documentation.