Setting up ISS-IUSERS when using a folder other than inetpub/wwwro

When setting up IIS in Vista (Home Premium) on my new laptop, I moved the
folder I use for my web pages to a subfolder of My Documents, instead of
under inetpub/wwwroot. I did this to make it easier to include any web pages
I have been working on when I do document backups. I use this server for
development purposes only, so don't need to have it available to users on the
Internet. I'm using Macromedia Homesite to develop and modify web pages.

I have been using this kind of folder (i.e. under My Documents) for my web
development pages for some time on my main desktop, which is still running
Windows 2000, however on the Vista machine, it has resulted in an "Error 500"
when I try to browse to localhost. Apparently, when setting up ISS, an
ISS_IUSERS net user is set up for wwwroot only. How can I set this user up
for the actual folder I use? ISS_IUSERS doesn't show up in the control panel
user account menu at all, but it does appear when I check the properties in
the wwwroot folder.
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Larry S