How do I change the way I open a piece of downloaded software.?

I tried to open a downloaded addon (for moviestorm), but I opened it in the wrong location, and accidentally set that as a default. how do I change it?How do I change the way I open a piece of downloaded software.?
Right click on the file and click ';Open With...';. Now you can choose the program you want to open the file. If it is not on the list, you can browse for it.

Or you could click Start -%26gt; Set Program Access and Defaults and choose one of the options.

Hope it helps.