Ubuntu took only 2GB, how to enlarge it?

[cyaquino]

My fresh Ubuntu 9.04 took only 2GB of free space, instead of the 40GB available . Now I cannot update anything because of "lack of space in /" .
How can I assign to it more empty disk space?
No place to open gparted:
system -> administration -> partition editor (doesn't show)

Thanks!

So it's a bug!!!!!!
Now I found http://ubuntuforums.org/showthread.php?t=1219270 with the solution. Thanks!!
And tell the guys to fix this annoying beginners experience!!!!!!!!!!!!!!!!!!!!!!