uTorrent is one of the best BitTorrent clients available for Windows. It is very powerful and efficient and full of features that will optimize your torrent needs like RSS auto-downloading, bandwidth prioritization, file transfers, and scheduling. It's by far one of the easiest torrent clients to use and is small enough to be ran off of a USB flash drive. The interface has a built in torrent search bar for fast torrent searching. uTorrent uses less than 6MB of memory so its not hogging all of your system resources. The uTorrent website will supply you with much more information. Here is the uTorrent download page.