Ok, that stuff couldn't possibly be better. It 100% isn't the modem, and I doubt it's your router's connection to it, given that this persists with multiple routers, but you have no problem with other networks.
I suspect one thing, but I haven't seen this issue since the days of Windows XP, so looking that crap up might take some time, if I can find it at all, and seeing if the solution can be applied to windows 7. And god only knows if that actually is the problem to begin with.
Google time.