You can use XAMPP, very easy to install an let you start your apache as service.
If you are looking for IIS to listen port 80 and apache on port 81, also you have to change apache SSL port, because IIS use 443.
If you want to use both on port 80, you can add to your Windows one virtual IP to the Local Conection, under TCP/IP Properties.
You will use your default static IP for IIS and the apache will use the virtual IP.
Then, add some entries on your c:\windows\system32\drivers\etc\hosts, like:
Try to start both services.
Ask me if you have further questions.