I have a old machine(pc) which doesn't contain os in it. (I can't boot it from pendrive or cd).
I want to install 14.04 over the local network on this device, as a server I could use a modern laptop with ubuntu gnome 14.04 I have.
I don't want to install ubuntu over the internet as it consumes my bandwidth :(
Can some say me how to do it with the iso i have in my modern computer in detail
I have tried to read the documentation of the Ubuntu but could not figure it on my own.
Download one of the installation ISO's, loop-back mount it, and serve it with a local HTTP/FTP server.
This will only work if you can boot the machine with a CD or USB, so no luck for you.
You could use a PXE installation, but that's non-trivial. If you don't know how to setup and configure DHCP/BOOTP, TFTP, and FTP/HTTP, look for other options.
Anyway, both methods are described in the source.
Source