µTorrent is an efficient and feature rich BitTorrent client for Windows sporting a very small footprint. It was designed to use as little cpu, memory and space as possible while offering all the functionality expected from advanced clients. 

Main Features: 

Multiple simultaneous downloads 

Smart bandwidth usage 

File level priorities 

Configurable bandwidth scheduling 

Global and per-torrent speed limiting 

Quickly resumes interrupted transfers 

UPnP support (WinXP only) 

Supports popular protocol extensions 

Localized to different languages