Security question re IIS_IUSERS

I set up my IIS default folder as a folder under My Documents, to make
backing up easier. I was able to get an IIS_IUSERS account set up for that
folder, but am wondering if that will somehow make my computer more
vulnerable. I am using IIS on this computer for web development only, and do
not need (or want) outside Internet access to it. I turned off sharing in
the folder properties. Is that enough to protect this computer when it is
hooked up to the Internet? Is there anything else I should do to make sure
this folder does not compromise security (or anything else I need to be sure
not to do!) ?

Thanks. Any feedback would be appreciated.
--
Larry S