Using
-XP(NTFS)
-IIS (the html folder has read, write permissions checked)

After typing in my info. doing the install I get:

Saving configuration data..
Could not write into mainfile.php. Please check the file permission and try again.

and at the top
Warning: copy(../mainfile.php): failed to open stream: Permission denied in F:\Inetpub\wwwroot\xoops-2.0.5\html\install\class\mainfilemanager.php on line 52

WHAT IS THE DEAL?
I also went into explore an gave rights to the folder and you can't un check the read-only box.