But how do I access the 'Special Stuff"? Every time I click it it reinstalls. Things like "Behind the scenes" and all that.

And then I found the answer, literally two minutes after posting, however now I've got another questiuon - how do I delete this post?

Okay, so this is where the extras are:
C:\Program Files (x86)\GalaxyClient\Games\!Downloads

It would be helpful if you could provide the answer so others with the same question can find the answer. :)

You can't delete forum posts and GOG.com Staff generally do not remove posts from threads.