That's right Windows isn't smart enough.
You're looking to "team" your two internet connections, which is possible but you must meet the following requirements:
A router/firewall supporting two connection and able to "team" them
Both connections would need to be with the same ISP, and said ISP would have to support teaming their end.
An alternative is use one connection for resilience, usually the slower of the two, the requirements for this would simply be a router supporting failover internet connections, such a router would be a Draytek Vigor 2820. This way if your primary connection drops you'll automatically switch to the other connection and switch back again when the primary connection reconnects.
[QUOTE=churin;434311]

Quote: Originally Posted by
DC187
Quote:
However if you want traffic destined to specific networks you could create some static routes in Windows to direct traffic over a specific gateway.
How can this be done? Could you point to any reference?
You can do this by using the route add command:
Open a cmd window and enter the following commands:
View existing routes:
route print
Add a new route:
route ADD x.x.x.x MASK x.x.x.x x.x.x.x METRIC 1
Where the first set of x.x.x.x is the destination network, the second group is the netmask and the third group is the gateway address this traffic will travel via
To make a route persistent across reboots add -p after the route command but before ADD
Use route -? for command help and usage.
I hope this helps in someway.