There are various references in the OpenInsight documents directory on the web for configuring Apache on Windows to run OECGI3.exe and O4W but some methods reffer to out-dated configuration directives or CGI only configurations. The blog DSig's Adventures in Revelation's O4W had an excellent summary of configuring O4W and Apache 2.2 but some of those configuration directives are out-dated in Apache 2.4.
Below is a current configuration snippet for Apache 2.4 on Windows. Simply change the paths to your O4W directory and add it to the bottom of your httpd.conf file or your vhost configuration.
Options Indexes FollowSymLinks ExecCGI
Require all granted
AddHandler cgi-script .exe
AddType text/html .exe
Alias /o4w/ "c:/revsoft/oinsight/o4w/"
Re-start Apache and verify http://localhost/o4w/start.htm loads and the Login link propertly executes OECGI3.exe and doesn't return a download file.