what is using port 80 ? maybe the windows IIS service ?
when there is no need for IIS shit .. disable/uninstall it
to change apache port do following (i expect u r using xammp)
go in folder /xampp/apache/conf/ and open/edit "httpd.conf" file.
then search for line "Listen" (should be line number 120).
should look like that
now change your port to the value you want to use for.
hope this help you ...