I have a PC (Window 7 Ultimate x64 SP1) with a time keeping problem. When Win7 is running the internal time gets behind 5 seconds every 10 minutes. This is a serious lag. The problem is pretty consistent. The system synchronizes its time every 10 minutes (because it is so inaccurate) with the atomic time servers and every synchronization interval the time is behind 5 seconds with just a few miliseconds variation between synchronization intervals. This is not a hardware problem, because when I boot the same system into XP maintenance partition the time is accurate. Actually, it is a few miliseconds ahead every 10 minutes, so this proves that there is nothing wrong with the motherboard. The problem is in Windows 7. From what I learned the time is kept internally by counting the hardware timer "ticks", so somehow Windows 7 is missing a lot of those ticks, while XP is OK in this respect. This problem happens regardless if W32Time service is running or not. Has anybody seen this behavior and knows how to fix it, or is it a Windows bug?