uTorrent implements many of the features introduced by much larger clients, but uTorrent retains a very small memory footprint. uTorrent’s typical memory usage is less than 6 MB, and the CPU use is low enough for most older systems (as low as 486) to run it. uTorrent is one of the most popular BiTorrent clients for PC users.

uTorrent (pronounced as ‘micro-torrent’, ‘you-torrent’ or ‘mu-torrent’) is a BitTorrent client for Microsoft Windows.

  • Micro-Sized Yet Feature Filled – Most of the features present in other BitTorrent clients are present in µTorrent, including bandwidth prioritization, scheduling, RSS auto-downloading and Mainline DHT (compatible with BitComet). Additionally, µTorrent supports the Protocol Encryption joint specification (compatible with Azureus 2.4.0.0, and now BitComet 0.63) and peer exchange.
  • Resource-Friendly – µTorrent was written with efficiency in mind. Unlike many torrent clients, it does not hog valuable system resources – typically using less than 6MB of memory, allowing you to use the computer as if it weren’t there at all. Additionally, the program itself is contained within a single executable less than 160 KB in size.
  • Skinnable and Localized – Various icon, toolbar graphic and status icon replacements are available, and creating your own is very simple. µTorrent also has support for localization, and with a language file present, will automatically switch to your system language. If your language isn’t available, you can easily add your own, or edit other existing translations to improve them!
  • Actively Developed and Improved – The developer puts in a lot of time working on features and making things more user-friendly. Releases only come out when they’re ready, with no schedule pressures, so the few bugs that appear are quickly addressed and fixed.

http://www.utorrent.com/