@RS singh
is there any problem with your internet connection? check out your system's network proxy.. If you are behind an ISA proxy then you might have to use NTLMAPS for requesting net access for your linux applications. Moreover, if you can't find apache2 , better option is to install it via automated process. try following:
sudo tasksel
then choose LAMP from the list and hit OK..
it will install Apache with all dependencies and configurations.
PRATIK ANAND