From a contribution I made to another forum:
My vote goes to shedding the 'brand affiliation' from the outset. there's not much point to it anymore, because with so much production being outsourced nowadays, almost every Brand Name laptop is simply a rebadged OEM unit, and all are of a similar quality. All of the Centrino laptops available, for example, are produced by one of only three manufacturers http://forums.pcpowerplay.com.au/ima.../icon_wink.gif
It's better to determine what you want to do with it, what configuration it needs to have, and what software/support bundle you need, then look at what's on the market that fits. Brand name is the LAST step in making the decision.
It's not a good idea to get your information from Sales people or personal contacts. Sales people are simply trying to sell you what they want to get rid of, and personal contacts often provide information which is personal opinion or outdated information.
Yes, it's true that some types of laptop are more conservative with power usage than others, but the P4/P3 comparison is a useless one. You simply don't find Pentium 3 laptops available for sale nowadays, unless you're buying a secondhand unit. All laptops use 'Mobile' processors. To date, they have been simply versions of their desktop processor equivalents which can run at lower voltage levels.
Recently, however, Intel has introduced a completely different processor series, and a form of laptop technology with it which uses power in a quite different way to earlier technologies. The PentiumM processor uses lower clockspeeds as well as power management to perform an equivalent amount of work, in an equivalent amount of time, with less battery consumption and longer battery life. The 'Centrino' laptop technology it's used in is a more expensive but more functional portable computer platform.
As I indicated in the quote above, work out what you need to use the laptop for, determine the features it needs to have, and then look at the available laptops to see which ones match your needs.
This belongs in the 'Hardware' section, by the way, so I'll move it there for you!
Cheers