Making an application portable

Dear members

I have read with interest how some have turned Skype and other applications portable. I'd be grateful if someone could explain why applications were written so that they impacted the registry when as we see with Portable Apps they could have written settings to the directory. It does seem to me that a lot of applications don't need to impact the registry so why were they written like this in the first place.

So what does one need to do to make an application portable or isn't it that easy. I have a copy of eMindMaps which i'd like to make portable. Later programs like Freemind, ThinkGraph are not as good, and the later MindManager far too complicated and less intuitive than eMindMaps.

I got the copy of eMindMaps from a magazine several years ago - another alternative is to contact MindManager and ask if they would be prepared to let someone from this forum have the code to convert it. MindManager have said to me that they don't mind eMindMaps being distributed as it is an older product.

many thanks