Okay server permission translations are pretty simple. I have done many an install on windows so let's break it down this way. Here is our installation instructions
http://www.photopost.com/installphp.html
Now here is the unix permission scale and what you need to set accordingly.
666 = READ WRITE
777 = READ WRITE EXECUTE
That should be all there is to it. Basically in windows if you want to make it ultra easy set your photopost directory to READ WRITE to get the config template and stylesheet files writable by the program. Then set your data and uploads directories to READ WRITE EXECUTE.