Wow, you guys have given me a lot to think about. From what I can tell thus far, it is mostly as DEL has described. Big loop around the house. The good thing is, each room on the first floor seems to drop to the basement, then tapped in series with the next room. So, it should be relatively simple for me to pull all new wires to 'home', heck, I can even move home to the basement based on this. Right now the 'home' is in a firewood closet in the living room, which, not a huge fan of.
So, aside from having the windows already drilled out, and cable running to those contacts, looks like I am not going to re-use much from the existing install. Based on what you guys have been saying, seems like it will be more work to figure out what is going on with all of them, rather than simply getting new contacts, and pulling new wire to the basement.
So, I may start with simply getting an ISY-994i, M1 Gold and some new window sensors for the first floor. See how that goes
Is this kit from Smarthome enough to get me going on that front?
http://www.smarthome.com/128301D/INSTEON-Compatible-Elk-M1-Gold-Kit-and-ISY-994i-with-Dual-Band-INSTEON-Interface/p.aspx