My suggestion would also be to go with Windows 64bit. Windows 32bit systems can only allocate a maximum 2 gigs of ram per program no matter how much ram is on the system.
I had problems with PD8 running on Vista 32 bit when I started trying to produce very complicated videos with multiple pip tracks and special effects on full 1920X1080 videos.
Lastly though know that editing 1920X1080 HD video even on desktop computers can really stretch them.
Bottom line if you are only using 1280X720 videos and do not want to do anything too fancy a powerful lap top should handle things.
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