Linux.... which one?

There are so many linux version out there. Current;y i’m using Mandrake.

I need a version which has the best security and compatibility. I am running a e-businese and plan to expand into a network. In hsort term around 5 computers. So as i’m doing e-commerce i need the best security, userinterface and compatibility.

which linux version/s would be best for:
-A network expecting to grow largerly in the near future. Looked at redhat linus looks sweet but very expensive (around $2500USD for the redhat network).
-Best security for e-commerce
-Runs All of windows software. In specific i need it to run Ebay toolbar and Ebay Turbolister. (you can check it out on their site which is free to download).
-Best GUI, I really want a system that is arranaged the same as windows. Like Windows XP how there is a My Computer, My Documents, Start, programs. I’ve use linux and i don’t like the way things are arranged and how you install programs, i don’t like it how they are group i like to see simply a folder of all the programs.
-I would prefer it to be free (or basic cost of cd). I wouldn’t mind paying for like 12 months support.

and that’s about it. I know that redhat and mandrake are pretty good and most of these things but they don’t support ALL windows software and the GUI is not my favour. I’m not the only one using it, i will have employees so i need the OS to be as if not EXACTLY like the common windows format. I will need to run adobe software.

thanks!