Ok, I am kinda confused. I had the idea that they sent us this letter because they could TELL that we were using two IPs. How can I just say we only have one machine? Is there no way for them to check? If not, then that's great...
As I said earlier, they can tell when you have a router, but as far as how many comps they wont know that, but if yer paying for 2 IPs right now, then they would assume that you only have 2 comps running off their bandwith. Bottom line, get a good router (I like Linksys myself) and cancel the 2nd IP and hook up all yer macs thru that router. ALso, if you can afford it, try getting a router that has 5 ports or more, dont get the usual 4 port, you will regret it; not b/c of performance as an issue, its just that if you decide to buy an airport basestation and xbox and PS2 and GC, etc etc etc, the 4 ports won't suffice.
I bought a sigle port linksys router and 16 port hub. It was more cost effective for me that way.
There you go!!