I use Win XP myself, made small game with it that i wanted others to test. Now my friend has Vista with latest service pack and always gets error that the exe is potentially harmful and does not open. He has admin permission for user as the only account on computer and tried to unblock best way he could.

What can i do to make file not seem harmful? Does exe need to have author details etc which i don't have, possibly some/any other files in directory to look less suspicious than single stand alone exe?