Hi chinna,
you don't need start admin server if you don't want.
the problem is with the WAS plugin mod_was_ap20_http.dll
look at \conf\httpd.conf file
Review that this two directives are correct (pointing to right paths and files), and the plugin file exists
LoadModule was_ap20_module "E:\WebSphere\Plugins\bin\32bits\mod_was_ap20_http.dll"
WebSpherePluginConfig "E:\WebSphere\Plugins\config\webserver1\plugin-cfg.xml"