Continuing to do a little basic research on the underlying causes of the problems here, I found a lot of discussion about the weaknesses of Windows and millisecond time control/reporting. It seems that standard Windows timing is done in ticks, which are about 55ms long under older Windows systems, and about 15ms under XP. There are some ways around this. I've included some links to relevant articles. High Performance Timing under Windows Obtaining Accurate Timestamps on Windows XP Inside Windows NT High Resolution Timers Dave G.