If you are using a BitTorrent client on a Windows XP computer, one of the things that will limit your speeds is that Windows XP SP2 limits the number TCP/IP half connections to 10. If you want to really speed up your Torrent downloads (and uploads), you need to increase this number. Here's one way to increase the number of half connections allowed in XP:

1 - Go to http://www.lvllord.de/?lang=en&url=downloads and download the patch file there (you can choose between English and German). Choose the option to save the file somewhere on your computer when you are downloading.

2 - Open the downloaded zip file (using something like WinZip) and run the executable inside. You'll get a bunch of warnings and confirmations. Just accept them all. Eventually a bunch of text will scroll by in an MS-DOS window and it'll wait for input. Type C.

3 - When it asks for the number of concurrent half-open connections, enter a much bigger number. I used 100 and got really good results.

4 - Depending on your setup, there may be more warning and/or confirmations. Just accept everything.

Once you are done, your TCP/IP will be patched to allow many more half-open connections and you should see a speed improvement in you torrent downloads.