I think points 2,3 and 6 would be standard on most decent spec machines.
Point 1 is simply software, IE7, Opera and I think, Firefox all provide tabbed browsing.
I think XP will reduce your options, as most new laptops seem to come with Vista, although XP machines can still be found but your choice will be limited.
no it doesn't have to be Intel, there are many AMD processors out there, but whoi is better, if anyone, varies from machine to machine, often dependent on other spec.
I'd be looking for around the 2Ghz speed range, minimum and maybe 3Mb RAM, but it all depends what you want the laptop for?