Avoid a Celeron chip if you can, they are not fast enough. Duel core cpu is ok, either Pentium or Centrino. The Pentium chips run very hot normally which means a heavy fan to cool them in most cases.
I have both as auxilary computers a Pentium 4 2.4Ghz laptop and a dual core Centrino laptop. The Centrino is by far the better unit because its light weight and smaller so can be carried around easier. The Pentium is a heavy weight and its fan is louder when it goes off which is every five minutes and stays on for ten. Horible when listening to music or watching a Dvd. When playing a game it can be very distracting.
In most cases the graphics card in laptops are slimed down versions of their desktop familly and therefore makes gaming a touchy experiance. On the box of my copy of Silent Hunter 4 is says:
Supported graphics cards:
ATI Radeon 9600/9700/9800/x300 to x850/x1300 to x1800
Nvidia Geforce 6200/6600/6800/7800
Laptop models of these cards may work but and are not supported.
When I bought my copy of SH3 I had a laptop as my main computer (the Pentium 4) and was gutted when it wouldnt play because its graphics card was not up to it. At that time SH3 spec was that it would run on any ATI Radeon card. It didnt run on mine because it was a laptop version of a Radeon! I had to when I could afford it build this desptop computer which is a monster before I could play it! I havnt tried to play it on my Duel core centrino laptop because I know its graphics card is not up to spec.
Also I would consider the sound quality issue. Most laptops have inferior sound as well.
Ah well just my 2p worth! A laptop is good as a back up mobile unit only!!
