Check your log, if it has something like this:
(OS 10048)Only one usage of each socket address (protocol/network address/port) is normally permitted. : make_sock: could not bind to address 0.0.0.0:80
no listening sockets available, shutting down
Check to see if you have SKYPE running. If so, shut down SKYPE and see if you can start Apache as a service.
http://www.tildemark.com/software/serve ... pache.html