Silverlight Evaluated Permission in Browser

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Silverlight

I am programming a silvelight application that is a Ftp manager like file zila.
this is my application image.




My Aplication Image





My left application part use Directory.Exist('x') Method that when my application start because it does not have evaluated permission, my left part application does not work.

I search the web and I found that I must sign my application and change a registery key but my users do ot understand it and can not do it.

Is any way that my application when start get evaluated Permission?