"When called from the command line, the ProcessIdleTasks work is done in the background asynchronously. It can take 10 to 15 minutes for idle tasks to complete. Task Manager will report processes running, and the disk will likely be active during this time"
The complete article can be found here:
http://www.microsoft.com/hwdev/platform ... chmark.asp
n the Run box, type "Rundll32.exe advapi32.dll,ProcessIdleTasks". This frees up any idle tasks running in the background so that Windows XP can devote its full attention to what you want it to do. For example playing graphic intensive games.