Before we start anything, I advise you to look at the Internet Security article in unchecking bindings in the Windows Network control panel. The first thing I want every user to understand is that there is no magic in getting 20mbps download speed on a 1mbps download speed pipe.
These days you won't be able to uncap (a step where the limit of amount of data being received and sent is switched to unlimited depending on the network speed, and is considered illegal by some ISP's like @home) your cable modem. DSL is a little different story where you are capped, depending on your line condition and how you may be able to handle a certain speed. When a DSL line's cap is raised, it could become unstable since too much data is being transferred at a long distance. Stay far away from any "hacks" or "patches" or certain "programs" that are suppose to make your connection much faster. They set your settings WAY too high and can cause only problems rather than fix anything.
Next step, we will take a look at what your computer already can do. IF you are close to 80% of your rated (advertised) speeds, then you are all fine!!! Go enjoy your connection! Now if you aren't, then do a speed test at dslreports.com
Below is what I received with my tweaked connection (ADSL 6mbps/128kbps).