are you using the server as a "real" server or as a localhost testing server? with a localhost server, just peek into your httpd.conf file, and set the "Listen" value to something else on 127.0.0.1... (and then restart apache)
I was installing apache, and ended up with 3 instances of the server running.. So, I set the first to "Listen 127.0.0.1:80", the second to "Listen 127.0.0.1:81" and the third to "Listen 127.0.0.1:82"...
obviously, to access each server, i had to use http://localhost:81 http://localhost:82 for the ones that weren't on port 80....
only reason I had that going is because I couldn't be bothered to restart my box... in general when I run apache I try and get it on 127.0.0.1:80....
did you run an apache instance and couldn't stop it?
do you run a firewall? if you do, you may need to allow apache to listen to a port.
do you run *nix? if you do, you need to be a superuser to start apache,,
EDT: oooh yeah.. the actual error would be helpful ^_-
