I'm not sure if this is the correct section. I've found this simple tweak to add a big difference to download speeds.
Run command prompt as administrator
Compound TCP - Improve throughput
Add-On Congestion Control Provider
The traditional slow-start and congestion avoidance algorithms in TCP help avoid network congestion by gradually increasing the TCP window at the beginning of transfers until the TCP Receive Window boundary is reached, or packet loss occurs. For broadband internet connections that combine high TCP Window with higher latency (high BDP), these algorithms do not increase the TCP windows fast enough to fully utilize the bandwidth of the connection.
Compound TCP (CTCP) is a newer method, available in Vista and Server 2008 (there is also a hotfix available for XP/2003). CTCP increases the TCP send window more aggressively for broadband connections (with large RWIN and BDP). CTCP attempts to maximize throughput by monitoring delay variations and packet loss. It also ensures that its behavior does not impact other TCP connections negatively.
By default, Vista and Windows 7 have CTCP turned off, it is only on by default under Server 2008. Turning this option on can significantly increase throughput.
To enable CTCP, in elevated command prompt type:
netsh int tcp set global congestionprovider=ctcp
To disable CTCP:
netsh int tcp set global congestionprovider=none
Possible options are: ctcp, none, default (restores the system default value).
Recommended setting: ctcp
It is better to use this newer generation CTCP congestion control algorithm for most broadband connections, we highly recommend it being turned on.