I am installing SugarCRM using sugarcrm-CE-6.4.2-linux-installer.bin file on a AWS ubuntu machine. This machine already has apache, will that instance be affected by SugarCRM intsaller?
I think you'll wind up with two instances of apache. To get the server without its dependencies get: http://www.sugarcrm.com/crm/download instead. (~19 MB zip file). But then you would have to configure your existing Apache to talk to it, and PHP MySQL etc. Apache says by default only one instance of the Daemon runs (configurable) so that means you would wind up with whichever started latest instead of two: http://www.jasny.net/articles/running-multiple-instances-of-apache/
Note: I'm not an expert and could have something wrong.