Ok, how do I check this? Of course, time and date displayed in the systray are correct. On the next reboot I can check Bios time although I don't see how this could be wrong time since I never changed it and I think it was ok before.
What services exactly do I have to check? I use a German Windows 7 version. Unfortunately the service names are German. But in their properties I can see the english name I think. There is a service called "Windows-Zeitgeber" (something like Windows-TimeGenerator in english), the name in properties is "W32Time". It is set to start "manually" (not automatically...?). But it IS started... so is here a problem?