Just a quick & dirty check can be to simply drop to a command prompt & use "netstat -an" & look for any "listening" connections on port 80/443. i.e.
TCP 0.0.0.0:80 0.0.0.0:0 LISTENING
TCP 0.0.0.0:443 0.0.0.0:0 LISTENING
or instead of 0.0.0.0 it also may be configured to listen on your specific IP address
TCP x.x.x.x:80 0.0.0.0:0 LISTENING
TCP x.x.x.x:443 0.0.0.0:0 LISTENING
or even on ipv6...
TCP [::]:80 [::]:0 LISTENING
TCP [::]:443 [::]:0 LISTENING
This would also show you if some other web-service was running, like apache or who knows what else. If you throw the -b option on netstat and it will also show you what executable is involved in creating the listening port. (the -b option requires elevated permissions just FYI)
One thing of note, it is not possible to have 2 separate applications (IIS & apache) both listen on the same ip address & port on the same machine.