If you're talking about dial-up, don't waste your money. All they do is build a bigger cache on your hard drive so previously visited pages load faster. They cannot change the physics of the telephone cable pair. See my page here for plain English information http://www.wayne.hardy.com/
Cable and DSL are a little different although they are analog signals just like dial-up. Some of the "Tweakers" may help, but I've seen no improvement. You can visit here http://www.broadbandreports.com/ for speed tests and a downloadable tweaker. Back up your registry before running the program.
Telephony facts, analog/digital explained.
See the CNet faces behind the posts.
I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image. - - Stephen W. Hawking
I've seen comments in the past that they provide quite limited benefit to speed. If that was the case, is it still? I'm trying out Netzero and PeoplePC and right now have opted for the accelerator in both, but I am wondering if I would be better of using the five bucks a month to buy a better grade of whiskey. grandpaw