Question : two ethernet to one motherboard, each ethernet is connected with a different isp. combination is needed

OS: windows 7 ultimate 64bit

i am subscribed to two isp's. I connected two ethernet cables from two different DSL routers to one motherboard that supports 2 ethernet interfaces. the two connections are enabled. windows 7 switches between them each time i use the internet. one is slower than the other. I had to disable the slower one to enjoy the faster connection provided by one of those isp's. How can i combine those two connections to increase the speed by combining the bandwith of these two connections  in order to enjoy faster browsing and downloading without the need for using a dual wan router? Load balancing was tried by me through dual wan router which gave the same result windows did (switching between these connections).

Answer : two ethernet to one motherboard, each ethernet is connected with a different isp. combination is needed

there is also "FULL" and "CROSS" joins