Pre-installed XP - no CD?

Hi,

I have never owned a laptop, and all my desktop machines (since I
abandoned windows at '98), have been home-built linux systems. I am
sorry, therefore, if my question is a really naive one. It is this - I am
going to have to get a fairly basic laptop running XP. Is it normally the
case that laptops have the OS pre-installed and come only with some
kind of back-up CD (not the actual OS)? I feel kind of naked without a
full copy of the OS available to me. Should I? Does practice vary
according to manufacturer/cost of machine, or do I just have to enquire
every time? The information does not seem to be easily available on most
vendors' sites.

Thanks,

Jim
.