The Portable for uTorrent, PortableApps' uTorrent is just such a program. It's a free, portable BitTorrent client that nevertheless includes most features common to peer-to-peer utilities, such as bandwidth prioritization, scheduling options, autodownloading of RSS feeds, and decentralized tracking through Mainline DHT. It typically uses less than 6MB of memory, which is insignificant to all systems but the most antiquated and is one of the keys to the program's total portability.

The license of this software is Freeware, you can free download and free use this file sharing software.