Why my laptop cant handle GOOD GAMES?, Desktop Athlon better than i5???!!!

Wanna ask some experts out there. Recently I bought a Lenovo G470 laptop.
The specs are:
Intel Core i5 2410M 2.3GHZ (TurboBoost to 2.9GHZ) Processor.
Integrated Intel HD Graphics ( AMD Radeon HD6370M 1GB)
RAM: 6GB DDR3
HDD: 600GB 5400RPM
Running Windows 7 Ultimate.

I tried Dead Island or NFS Most Wanted 2012 but both lagging on my laptop. So I tried some old games. ( CALL OF DUTY: MODERN WARFARE 2). The games seems got some spike lag. ( MEANS LAGGY TOO).

I got another Desktop.
AMD Athlon x2 1.8GHZ
NVIDIA 9500GT 512MB
RAM: 4GB DDR2
HDD: 160GB
Running Windows XP

I tried CALL OF DUTY: MODERN WARFARE 2 on it and it doesnt lag at all?


How come the AMD Athlon can run more smooth than the i5 2nd Gen processor? Any advise?