Dell XPS14 FPS drops and concers

i bought DELL XPS 14 (L401x) 2 years ago it began to have some troubles after a year so i sent it to technical support guarantee and got almost all hardware replaced.

laptop runned fine for almost a year then.
run diablo 3 and all kind of ps3 games whit no problem
thing is it began to overheat and shutdown, fps drops and audio shuttering a while ago so i cleaned it and bought a cooling base
now it dosent shutsdown, no audio shuttering but has constant fps drops making games unplayable.

thing is dosent matter the graphis set on the game it will always have the same fps drops on high medium or low i dont know what to do about it

i ran the 3dmark vantage and here are my results please help.

Computer Technical Sheet:

Windows 7 x64 Bits
Nvidia Gforce 420M 1GB
Intel core i5 2.8 Ghz - 3.2 Turbo Boost
6Gb Ram
500GB HDD

NVIDIA GeForce GT 420M video card benchmark result - Intel Core i5-480M Processor,Dell Inc. 011NDY score: P3624 3DMarks

sorry for the bad english i hope u can help me out

PD: i just updated nvidia driver from nvidia sources (same fps drops)

latencymon shows me this problem is dell webpage dont have bios updates and i really dont know which BIOS to install plz someone that knows about this help me