Thanks keef, and that is the big question. I don't fully understand the differences, however I believe that professional is more compatible with XP programmes and files and that there is better security and remote access functionality.
I will have an XP desk top with Acrobat Professional 7, OS map routing software (which I may put on the laptop) and I will occasionally be using it on a network which has XP machine, I will aslo be using it for remote access to a company accounts software package on their server.
Essentially these are the reasons I believe professional would be the better option.