XPS 15 Slowdowns while gaming

Hello, I have purchased this XPS Laptop about 7 months ago. I purchased it with the intent of gaming and work, with a little travel here and there. The laptop worked great out of the box. After about a month or so, I started to encounter these laptop slowdowns during heavy gaming, where my frame-rate drops from 60fps to about 3-5fps with sound cutting in and out, lasting about a minute in 5 minute to 30 minute intervals. This only affected the taxing games on the XPS, eg. Mass Effect 2, Starcraft 2, BF: Bad Company 2, etc. As time went on this started to effect my more simple games like, Counter Strike: Condition Zero, MineCraft, and World of Warcraft. This is very disappointing because now I have to turn my graphic settings to minimal(They weren't very high to begin with), and I am still encountering problems.

After some research, I have come to the conclusion that it is my CPU overheating, so it has to power down to lower heat. My question is, why is the cooling not ample enough to keep cool under gaming conditions? This laptop was built with the intent of gaming and performance, was it not? How may I be able to fix this problem?

I have reset the laptop to factory setting and am still seeing the same issue. The BIOS is up to date as well as all the drivers. I rarely use it with out it being powered by the AC Adapter. I have gotten the blue screen of death a few times.

My Specs

XPS L401x

Windows 7(64bit)

Intel Core i7 CPU q 740 @1.73gGHz

4gb of RAM (Two 2048 MB DDR3 1333 MHz)

NVIDIA GeForce GT 425M (2gb Video Memory)