Sounds like you have sort of the same issue I have, but mine is 100 times worse than yours since my lappy isn’t even close to being a gaming lap. But I use this auto exec config made for low end computers and it is the only way I am able to play.
http://forums.steampowered.com/forums/show…ad.php?t=523089
It turns stuff way down, but its not too too bad to play with…maybe give it a go? Couldn’t hurt I don’t think…