if you are going to take your notebook around, you will appriciate a lighter notobook. in my opinion, if you alrady have a desktop and the notebook is your second computer, i recommend you get a light one. if it is going to be your only computer, get a full function one (include a cd or dvd rom but not floppy, in my opinion)

general speaking, taiwan made computer is pretty good in quality. but not as good as a japan made or usa made.

a 10.4 screan is too small in my opinion. at least get a 12 inch one. not to meantion the keyboard is more comfortable in 12 inch machine.

get one from big name, and that will save you a lot of trouble. i mean BIG name. like sony, toshiba, ibm, compaq... and so on.

depends on usage. for daily useage. processer speed is NOT that important. no need to go for the fastest one. however, try to get as much RAM as possible. at least 256mb for WinXP. if possible, 512mb is even better.

in your list:
sony sr7 is made in japan and the quality is excellent. but there are 3 drewback. 1. it doesn't come standard with a ethernet port, so you have to buy a pcmcia version. and that machine only come with one type2 slot. 2. the screan is only 10.4 inch. 3. the ram is not standard sodimm. it's micro so-dimm. which is much more expensive than sodimm.

toshiba 4000 is excellent. just more expensive.

omibook 500 is a fine machine. you can use it as dasktop and notebook once you get the base.

if possible, look for pIII-M which has 512k of casche and .13 die (which runs cooler)