Boracay, the question is what do you need it to do?
And then you work backwards from there. If Linux is a priority, you decide what flavor you are going to use and then find out what notebooks support that--or live in driver hell.
Do you want low power consumption
? Then you are looking for a 10-12" screen
. High resolution for charting? Maybe 15" 19xx/1080 screen. Gobs of power and you want to watch movies as well? 18" screen.
Do you type or word process? HP makes great laptops, funny
keyboards. Lenovo, great keyboards. Check the price
with a 3 year "depot" warranty, Dell may be cheaper than those two--but costs more when you add up the extras. (And I hate Dell anyway.)
XP is no longer supported, there will be no security
updates for it. Your laptop will come with Vista or Win7 and that's simply life, unless you can get a bare system from someone like Lenovo. Which is probably a mistake because you'll want a Windows OS to dual boot, odds are. Everything doesn't run under Linux.
Serial ports ain't gonna happen. You'll buy a usb-serial adapter, that is logo certified for your OS because the uncertified ones are less likely to work well. Or, a PCM (or other) slot adapter to do the job. Those are the most expensive and most robust.
There's also no NMEA input on computers
. Serial input was equivalent but that's just not going to be found on anything made in the last 5 years. The adapter does it.
And you want an SD-HD card reader built it, very very handy to move backups to your GPS
or cell phone
The rest depends on what you need the machine to do, and work with. They'll pretty much all have DVD built in, look for a writer not just a reader. You won't get BluRay (reader or writer) yet without paying a steep premium. WiFi will be in almost everything, quality varies but that's the tail wagging the dog, you can get outboard
WiFi that will have much higher range.
Batteries, battery options, docks, audio (if you want it to be your media center)...and of course the price
you aren't willing to exceed. Processors? Anything probably will do these days, more gets you faster but even the low end is fast these days, unless you're doing photo
editing or other intense tasks on it.