Display Networked Computers

I have a vpn connecting three offices with about 20 pcs which has all of the pc's networked together.

I need to do one of two things:
1. List all of the computers on the network, and/or
2. Detect if a certain pc is connected via ping (i know the ip address and pc name).

I'm using vb .net and am new to this. All my work so far has been borrowed from other example vbprojects, so any instructions have to be pretty basic :).

The project I'm creating is so that my users in the remote offices can download two .mdb files to a laptop. I have a project that will zip the files and copy them to a destination, but now I need them to select the laptop to copy the files to, or at least confirm that they have plugged it into the network (they are computer illiterate).

THanks in advance!