One hint is to turn off Virtual Memory. This has been known to shave 2-3ms off your latency.

Right-click on My Computer, go to Properties, Performance, Virtual Memory.
Choose "Let Me Specify my own Virtual Memory Settings"
Then choose "Disable Virtual Memory." Windows will give you a warning box that this is not recommended. That's ok- this was from back in the day where PCs had 32 or 64mb of ram.
Restart your computer.