Fastest way to set up running cron job task on Windows Server is adding Scheduled Task by using command line.
Open your cmd (with admin rights if possible) and enter this line
schtasks /create /tn "Generate sitemap" /tr "C:\PR OGRA~1\MOZILL~1\firefox.exe http://example.com/cron-job" /sc daily
This command will create scheduled task named "Generate sitemap" and it will call http://example.com/cron-job daily