http://www.speedguide.net/downloads.php
1) Download "TCP Optimizer"
2) Go to www.speedtest.net and run a speed test.
3) Open TCP Optimizer, select "optimal settings" in the bottom right corner
4) Apply/restart
5) Go back to www.speedtest.net , compare results, dance 
NOTE: Results may very, but typically a 300% DL gain.
Test subjects (all with Cox cable, high speed internet):
-Vista laptop, wireless. Negative affect.
-XP laptop, wireless. Download went from [6088kb/s DL / 555kb/s UL] to [19278kb/s DL / 558kb/s UL]
-XP Desktop, direct-connect. Download went from [12581kb/s DL / 560kb/s UL] to [23356kb/s DL / 558kb/s UL]
Enjoy. Please post your before and after results.