Yes, the HD case sounds like a good idea. USB keys are useful, have
limitations when it comes to large files. You can resize your partitions
from Gparted or Partition Editor, as long as it is not mounted. For that you
need to be working from another file system or the Live CD. Windows will
even work provided you have the right software. I like Parted Magic Live CD
which I always keep a copy around. You never know when you will need it. I
use rewritables so that I can upgrade the version as needed.

It is probably easier just to delete the existing partitions and start over
without any partitioning. It is the best of limited space.