How to limit internet bandwith

You can use Traffic Shaper XP: http://bandwidthcontroller.com/trafficShaperXp.html , which is free.
There is also http://www.netlimiter.com/ which is not free.

You can use http://readerror.gmxhome.de/ netmeter to watch your current bandwith.
For other downloads you can use free download manager: http://www.freedownloadmanager.org which can
set bandwith for current file on local computer. (In advanced options.)