I understand how hard it is for players, and developers to freshly install a game (whether it be theirs, or not) from anywhere only to see it not work, and I've had my fare share of those happen just as much as everyone else here more recently though was with Warlords of Dreanor from the Firestorm servers now don't get me wrong, I love Firestorm, but even though "I love them" that doesn't mean them perfect, far from it in fact. They are only human, just like the rest of us, and they will make mistakes, again just like the rest of us that's why it's up to us as a community to help resolve whatever we can whenever we can, to make the Forum, and the game a better place to co-exist in.
"Enough rambling Vexes, and tell us what we came here for!" you might be saying, and ok I'll give you a quick run down of what you most likely came here for.
Why I think This Exists & How To Fix It
As you all know since Firestorm released 6.2.3 they've been "plagued" with error reports from people who freshly installed the game through the Firestorm launcher they attempted to use a torrent (With little success IMO) to resolve this issue thinking it was some issue with installing all the needed files which they where kinda correct, but the "fix" at times proved to not work for some people, because of one small thing they overlooked as far as I can see from the forum anyway, the reason for the error is mainly because the client cannot finish writing data to the folder because the folder has a Read Only Permission which is easily fixed by Right Clicking, and going down to Properties then un-checking the Read Only option near the bottom of the General Page once that is done you should be able to load the game just like normal, and have some fun in Azeroth once again with Firestorm
Step By Step Photo Tutorial