Open httpd.conf of Apache server (backup first)
Look for the the following : Listen
Change the line to 
Listen *:80
Still in httpd.conf, look for the following (or similar):
<Directory />
    Options FollowSymLinks
    AllowOverride None
    Order deny,allow
    Allow from all
    Deny from all
</Directory>
Change this block to :
<Directory />
    Options FollowSymLinks
    AllowOverride None
    Order deny,allow
    Allow from all
    #Deny from all
</Directory>
Save httpd.conf and restart apache
Open port 80 of the server such that everyone can access your server.
Open Control Panel  >> System and Security >> Windows Firewall then click on “Advance Setting” and then select “Inbound Rules” from the left panel and then click on “Add Rule…”. Select “PORT” as an option from the list and then in the next screen select “TCP” protocol and enter port number “80” under “Specific local port” then click on the ”Next” button and select “Allow the Connection” and then give the general name and description to this port and click Done.
Restart WAMP and access your machine in LAN or WAN.