(Gonna boot this one over to Support.)
With the exception of that video card, those specs are no worse than my own desktop system (in fact, depending on what variant you have, that card may have more memory than mine), and I can run everything outside of MV_Advanced with no major slowdowns. Your laptop certainly has far more than enough firepower to run the retail game. There has to be something leaking memory, whether it's the game itself or some other program that's getting triggered by it. Have you tried disabling any anti-virus/anti-spyware software you have running?