Quite all right. I'm glad that you're protected. You can rest easier in knowing that the newest version of ZoneAlarm Free does protect mobile users as well as fixed installations.
As for WinPatrol, you're right, it's a great program. I'm a registered user of WinPatrol Plus.
Unfortunately, the only place I can point to your error is the idea that an integrated program will result in less processor overhead. That is not always the case. Even these days, it's remarkably hard to judge how much of a load a particular program puts on your system. If you have a reasonably modern system (CPU speed over 1 GHz), then it really shouldn't make a big difference to your system's performance. I have to admit that I have a hard time imagining where running firewall software would be noticeable, except if you were running a few of the most modern games on an older system with outdated hardware. If that's the case, then you have more problems than security software.
As for the ISP, that's exactly what happens. Their servers do the routing to the actual customers' lines and what you think is your IP is not necessarily going to remain the same the next time you log in. That goes double if you're using DSL, since you dial in every time you go to connect (as I understand it).
As you note, it still can't stop Bad Guys from going after your system, if they want to. Your system, after all, does have an IP address, however temporary. Your vulnerability exists because these crackers run software that probes huge numbers of IP's, one by one in order. Sooner or later, they'll get to YOU. As soon as they get a response, other software goes to work and you're under attack. The good thing about firewalls like ZoneAlarm is that they try to keep anyone out there from getting a response from your system. They do it by ignoring most outside requests. The only ones they let through are- #1) Requests generated by you or your software, or #2) connection maintenance traffic generated by your ISP (and even that is monitored). The birth of what are called 'Blended threats' has upped the battle. Then throw in spoofing and all the other threats and you can be sure that the wages that security experts get is well earned. Top that off with the fact that the threats change on an almost hourly basis...
Now, how does all this apply to your original plan of buying a laptop. This becomes a little subjective, but I can offer a few guidelines, I think. First, I'd look for no less than a 1.5 GHz (P4M) or 1500+ Athlon CPU. Any less than that and you're not going to get performance you want. It's really tough having a decently fast desktop and then trying to get used to losing half that performance every time you turn on the laptop. I'm going to be in the market for one, myself, so I know what's going on. Fortunately, prices are coming down all the time. I've seen reasonable prices on 2200+ laptops, lately. Second, I wouldn't settle for any less than 256 megs of RAM aand I'd make sure that adding RAM was something I could do without taking it in for service.
Then you add in a 40 gig minimum hard drive, USB 2.0 ports, and the rest of the goodies.
That should give you a good shot at running whatever you want to without worrying too much about CPU load.
=== SHOPPINGMAN!!! Never assume ANYTHING ====