Strong Bad?
On topic: I am on a laptop with onboard video (Mobile Intel 4 Series Express) and 3GB of RAM. I can run indoor sections of Episode 2 (Our Mutual Fiend, etc) acceptably. It’s not smooth and beautiful and I have to use low settings, but it’s not a slideshow either. In fact, most of Ep 2 was acceptable. The only portion that wasn’t was the strider battle in White Forest. Slideshow City. > 
I believe BM will run acceptably on this laptop as, as far as I know, there aren’t too many extremely wide open sections in the entire HL game – Xen doesn’t really count too much because there wasn’t much in the outdoor sections. I could be wrong.
I was playing Ep 2 a bit ago and when the hunters were attacking inside the silo of Our Mutual Fiend, it was smooth as silk, believe it or not. I think that the inside sections of OMF is possibly an acceptable benchmark for BM. But, again, I could be wrong.