Intel GMA 4500mhd driver update problem?

I have a Sony Vaio laptop and I have been trying to update my drivers for my Intel 4500MHD card for a while now. When I try to get the update from intel, I get the an error saying that my card has a custom driver from Sony, that I cannot proceed with the current driver update and I should get my driver update from Sony. However, Sony hasn't released an update for this card and performance in games is quite lacking. To counter this, I uninstalled the drivers that came with the computer and then installed the more recent drivers. Performance in Left 4 Dead has gone from 4 - 30 FPS to 15 - 50 FPS, even when I went from 600x480 to 800x600 resolution. The card has been injected with steroids. My problem is that I should not be getting such performance from this card. I am absolutely sure that I downloaded the correct drivers and I am aware that a boost in performance is expected with a driver update but it seems too good to be true. I love the performance I'm getting, but I'll roll back the drivers if I'm damaging my computer. What do you think?