For the last few weeks, I've been running with Windows registry settings tweaked by the TCP Optimizer program. The TCPOptimizer.exe program sets a collection of apparently widely-known registry settings that 'open up the pipe' on the client side.
I'm currently running with Windows XP Professional. If you are running Vista, I can't help you. ;)
Vista
Vista shouldn't need optimization; its IP stack is much more aggressive about real-time tuning for the current conditions.