Without a network connection, coLinux won't be very useful. However, since it runs within Windows and is supposed to cooperate, it won't just steal access to the network. Instead, it acts as a separate computer connected over a network. The TAP-Win32 network driver is an odd little thing that allows a process in your computer (i.e., coLinux) to connect to your computer (Windows) as if it were a separate computer connected over a network. This way, you have a connection shared between Windows and coLinux with relatively little trouble.