Limiting bandwidth over the LAN can be done in windows, but limiting INTERNET bandwidth cannot be done in windows.
Windows bandwidth is only 20 percent of the network speed for that system only. So it's rather useless, unless a router is filtering first. Anyway that's all confusing without actually knowing about it lol.
You may be able to find a program via Google search. But I doubt there is one for Win7 yet. It's hard to find a good one for XP.