The Windoze technical info states that they do not guarantee timing better than 100ms with the system clock. You're right, that generally it's much better than that, but I have seen pauses in my VIs that vary up to 25ms (using a take time before the loop and then check time after the loop). My old Windoze 98 machine varied by as much as 75ms. Yes, NT and XP are better for timing, but there are still no promises. If it's really critical, use hardware (like you said).
Rob
