How to connect two virtual machines with two different networks?

Hello,
use the Virtual Network Editor program (accessible from the Windows Start menu) to add a new network (Add Network).

1) choose "Host-only (connect VMs internally in a private network)" to create an internal network (a switch, really).
2) uncheck the box "Connect a host virtual adapter to this network"
3) If you want IP addresses to be distributed automatically, you can leave the box "Use local DHCP service to distribute IP address to VMs" and configure it via the "DHCP Settings" button.
OR INSTEAD, uncheck this box and assign static IPs to your VMs from the guest system (installed in the VM).

4) Now that you have your new virtual switch, you just need to add a new virtual network adapter on your VMs and choose the network "VMnetx" (created in Virtual Network Editor) in the "Custom: Specific virtual network" list.

PS: if you need a small clarification for VMware, don't hesitate to ask me ;-)