L4D2 lags and hangs, didn't use to, and I use an i7. Help?

Recently i had my laptops harddrive, heatsink and fan replaced because of overheating (i guess it was because it burned the harddrive and killed it.. or something like that )... Sort-of-fluff substance builds up on the fan (there was LOADS on mine) - you can either buy something that cleans the inside (air-horn type thing or whatever) or open it up and clean it yourself. Suprisingly my laptop overheats on l4d2 so i use a fan-cooling mat and another fan on the battery pack place to cool it down - which works... but still gets 80degrees celsius

What laptop do you have?

(and where do you live? )

 

Luke:
The problem was with the heating. I never had problems with my laptop before. It was good enough to play Crysis on High settings and L4D2 was a joke for the GPU/CPU. Recently it started lagging, and surprisingly, it was the temperature.

Now I have a fan blowing on my laptop, and I placed a book underneath it to make more room for its internal fans.
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Bro that it is a big problem , you play with "CLASS 3" video card on one laptop wich is not made for the hard gaming.First at all if you want play games on laptop should buy gaming laptop. And before you buy new laptop one time ,when you have money check first graphics inside machine , you will always have problems it's not only the heat trust me.

http://www.notebookcheck.net/Comparison-of-Laptop-Graphics-Cards.130.0.html

Many cheap deals now from Asus G50 series with gtx 560m 2 -3 gb memory cards