The problem may not be Windows, may not be your DSL, nor may be it your computer. It may be other things; trojan horse applications, hijacked HTTP sessions, or other things.
What may be happening to your bandwidth is this:
When you type in
http://www.scubaboard.com you expect a request from your computer to go directly to the web server(s) housing the scubaboard website and for those servers to reply back to your request, sending the data from their server(s) back to your machine.
What is most likely happening is that there is an (or several) application that are running in the background, unbeknownst to you, that hijack your http sessions. When you type in
http://www.scubaboard.com (or any web site, or click on any link), these little programs redirect your request to Company X's servers, where they read a cookie (file) on your machine, listing your Internet Address, the name of the site you're attempting to browse to, and some other things, and they put that information into a database. Once that information is stored, they then forward your request to the site you're looking for, and then reply to you with the page you requested. This is called hijacking. It's typically used to build a profile of what types of sites you visit, so they can sell advertising via POPUP windows. Not all Internet browsers make it easy to do this. As mentioned above, Mozilla does not. There are others like Opera that do not as well. Although changing browsers may solve some issues, this also creates several issues on it's own, and most people that I know that use Opera or Mozilla, end up using Internet Explorer more times than not.
Visit this site, "
http://www.safer-networking.org/ "download and run the application SPYBOT SEARCH AND DESTROY, run the UPDATE, and then tell it to "Find Problems". Once it's found the 200 or so issues with your computer, clean up the problems (can be done clicking on one button), and then when finished, immunize against these issues so you don't have them in the future. You'll be very surprised to see what's going on behind all the eye candy of web pages, and you'll notice a faster browsing experience immediatly. Best of all, it's free.
If you have problems with popup advertisements, you can try the google toolbar also. you can find it at toolbar.google.com. It adds a toolbar to IE, and has a builtin popup killer that works very well, and is free.
PM me if you have questions