This is a nice-sounding tweak, but to clarify, Windows is NOT always reserving 20% of your bandwidth for downloading updates--only when automatic updates is currently downloading an update. I didn't notice if anyone above said this or not. And regardless, updates are not so huge that you'd even notice your internet lagging (to a certain extent). As long as Windows is not updating itself, you will have access to 100% of your available bandwidth. It's not like an actual internet tweak that will provide higher bandwidth. Might as well leave well enough alone unless you need 100% of your bandwidth 100% of the time. Just wanted to clear up that possible confusion.

On a second point, I'm not sure if a lot of you all know this, but the best way to notice better bandwidth is to change your MaxMTU, RWIN and TTL values of your NIC to be optimized for your particular ISP and modem/router/gateway. Windows default values are typically optimized for dial-up modem users--things such as packet size and dwell time. You can do this in the registry (bad idea if you're not sure of what you're doing), or better yet, use a program like TweakDUN, which is a free program (or was--haven't checked recently), and also has a real-time bandwidth meter built into the program. Just FYI. Cheers!