I just want to point out that I when I try to play online on my laptop, (which happens to have Windows 7, as irrelevant as it probably is) it too is horribly laggish whenever I move, but not when I stand still. The laptop is in the same house, connected to all the same stuff, heck, it's even a much more capable computer, but it cannot handle online SRB2 for some reason. Single Player is fine though, it's just Multiplayer. And no, it wasn't the server I connected to, because it does it on all of them. Just thought I might point this out just to back up the OP's claim. Perhaps I should try OpenGL on it and see what happens then...