ISAPI_Rewrite is Apache mod_rewrite compatible URL rewriter for Microsoft IIS server. "ISAPI_Rewrite supports .htaccess files that can uppear in any directory inside a web site and rules from these files will apply to this location and subdirectories. All configuration files are reloaded automatically every time the file is changed. It is allowed to change file content from third party programs and scripts." http://www.helicontech.com/download-isapi_rewrite3.htm
add this to the .htaccess file to set the base directory for rewriting.
# temporarily set the base directory
# before domain is working