I have been following your thread here:
As I said in my last post in that thread, your /usr directory is 7GB. This is likely the problem, since your root partition is only 10GB. Do you have any big programs like 3D games installed on your system? If so, then you may need to remove some programs to free up some space. Either that or you could use GParted on the Ubuntu live CD to shrink one of your other partitions and grow Ubuntu's root partition into the unallocated space after you free up some space. You could shrink the Windows7 partition. You also have a lot of free space on /home. The /boot directory is in the way though. I'm not sure if you could grow root into that partition with /boot in between them.
Post the output of these 2 commands:
sudo du -csh /usr/*
sudo du -csh /usr/local/*
Also, as I said in the Ubuntu forums thread, you can free up a bit of space in /var with:
sudo apt-get autoclean
or to free up more space: