Yeah i noticed that after i posted, so it's not so terrible.
Still, i'm partially using the VM like a nuclear test bunker to run dodgy sites and software I don't want in the main OS... I don't want a worm or something escaping the VM through the Users folder!
I removed the perms and...
I was trying to share some stuff between win 8 and my new hyper-v VM of XP, and noticed the Win8 Users folder is already set to allow Everyone read/write permissions! That can't be right surely? If I turn this off will it break anything?