I can solve one mystery at least: 192.168.2.3 is a private address being used on the small local network formed by your wireless box and your computers. Any address in the range 192.168.*.* is considered private, and isn't "routed" on the Internet--that is, nobody can connect directly to that address. Instead, the wireless box does an address translation, between the address your ISP issued to it, and the 192.168.*.* private addresses.

Bottom line: That's normal.

You mention that it says that security is disabled. Depending on exactly what that means, it could be possible for somebody (a neighbor, somebody driving by) to connect to your wireless system and use your Internet service, and possibly to get into your computers. Most viruses are spread by email, but an open wireless system is a second possible infection vector.

You need to lock down your wireless security. Probably best to ask the local Geek to do it, because the method depends on the equipment. In general you should enable encryption and configure the wireless box to communicate only with specific computers (yours).

The fact that the wireless network in your home connects your computers to each other opens up another vulnerability: The infected computer might infect other computers. It sounds like it might be too late, but you should try to avoid powering up the (previously) uninfected computers at the same time as the infected computer.

Good luck, Lindy!