The new Wireless N USB Adapter from TRENDnet (TEW-684UB) is Dual Band and supports the latest 450Mbps technology. Its shape is very similar to the 450Mbps Gaming Adapter, also from TRENDnet, but its much smaller and does not require extra power, coming with USB connectivity.
Slow computer got you down? Maybe a hardware upgrade should be in your cards, if so this guide to the Fundamentals of Upgrading a PC is an invaluable read. PCSTATS Tips