http://forums.guru3d.com/showthread.php?t=376458TimerResolution is an application to change the resolution of the default windows timer. The standard timer on Windows XP can vary between 10 and 25 milliseconds. Therefore if your code uses a timer or sleep value less than the timer resolution on your system you won’t be getting the results you expect.
I'm curious what effects reducing the timer resolution could have on input lag. It reduces DPC Latency dramatically for me, but has no significant effect on FPS (according to TF2 benchmarks) that's about all I can confirm.