Hello.
Did you ever tried QtParted? I think this is a VERY powerful partitioner, and it can and will help you. Once I installed Solaris on an empty HDD, and the Solaris partitioner made something bad. I could not use my HDD any more. Then I tried Partition magic 8 but it could not do anything. I thought my HDD can be thrown out. But no! QtParted could fix it (I had a workin Linux on my PC), and now I'm using it as an external USB HDD like you. If you have an internet connection I think it won't be a problem to install it. Their homepage is here:
http://qtparted.sourceforge.net/ A good advice for you: If you ever write a post like this, when a prog is needed, it is recommended to write your Linux distro. It is useful. OR, you can set in your LQ profile, so, anybody looks on your post, will see what distro you are using. Trust me: it helps. Good luck!