You can custom build a laptop - it's not seen very often though. Most custom built machines are desktop versions.

As for processor, I'm not really a fan of anything but Intel Pentium (don't like AMD or Celeron).

I myself have a Sony that I bought off the net. Supposedly is refurbished, but never had any problems with it.

As for screen size, kind of depends on what you'll be doing with it. There are some out there now that have a 15.7 SXGA TFT display which is good if you'll be watching movies all the time on there. If you'll be hooking it up to another component (TV) to watch it, then size won't really matter.

Not sure about the others, but I know Sony enalbes you to take out your floppy drive and add a 2nd battery for longer life. Definitely good for watching DVD's on a flight.

DVD - go ahead and get the DVD / CD-RW burner combo drive

Video output - with video output (it's the yellow one) you can just connect a cord and hook it up to your tv. i use my sony vaio with it and watch DVD's on my television.

OS - kind of depends on what you like. believe most will be standard with XP now. i still run 98 SE (most reliable out there besides the Apple Mac)

12-20gig(or more) - kind of depends on what you'll be doing. like someone said before, if you're into mp3's and all that, get at least a 40 gig. but if you're not doing much, then a 20 gig or 30 gig is sufficient.

CAT-5 port - not really necessary unless you have cable or DSL (ethernet). if you want, you can just buy a separate network card. but if you're looking to cut down all the extra crap to tag around with your pc, then get one that's got in installed.

memory (128?) - more you have the more efficient & quicker programs will load. at least 256 is recommended, especially if you're running XP.