This laptop - now replaced by my Macbook - was purchased mainly to cover my requirement for mobile computing between selling my old laptop and getting my Macbook. As far as specifications go, by todays standard it is outdated, however, only occasionally noticeable.
The pentium 4 processor is now outdated, however, it is more than enough for browsing the web and using basic productivity applications. Don't purchase one expecting a powerhouse as all you will get is a very basic computer for little cash.
The laptop is as upgradable as any other - i.e. memory and hard drive, thats it. The memory can take up to 1.5GB which is pretty impressive considering the age of the computer.
My N4000 arrived with Xp pro installed, performance was predictably unimpressive and boot up times were very long.
The overall build quality was poor as after just two days the hinge had broken resulting in use of the warranty straight away - not a good start.
Battery life was equally unimpressive, lasting just 2 hours.
Overall, if you need a basic laptop i would say look elsewhere.