Mark Russinovich at www.sysinternals.com has released freeware utility Frob that allows you to sets NT foreground and background quanta. Useful to Windows NT admin.

One of the most annoying characteristics of NT is its lack of support for tuning various system performance settings such as the foreground and background process quanta (a quantum is the time-slice, or length of time a thread will run without being pulled off the CPU for another thread to run). On NT Server, the quanta are fixed for both foreground and background processes at 120ms, and on NT Workstation a background process has a quantum of 20ms, and a foreground process has a quantum of either 20, 40, or 60ms (the foreground boost slider in the Performance tab of the System applet in the Control Panel determines which). Well, here's a little applet that will let you "frob" the quanta to your liking. The new quanta will immediately be applied to every process in the system and will also affect new processes that are created.