Dell Studio XPS 16 with Intel Core i7, 4 Gbyte RAM and ATI Mobility Radeon HD 4670 not able to play 2011 game releases lag free

Hi

I bought this Dell Studio XPS 16 in 2010 as a gaming laptop (as rated as one of the top 5) and in 2011 started having trouble playing Witcher 2 and Elder Scrolls V: Skyrim without lagging. It is such severe lagging that it makes game play unbearable. I have no idea how to start with the problem, I have done extensive research on many chat boards about how to fix the problem but found myself in a never ending rabbit hole of new problems.

If someone could tell me if my laptop hardware is sufficient to play these games, and if it is why I am experiencing this problem. I have tried to locate a bottle neck in my performance, but found none.

Any help would be greatly appreciated!