The time would not stay synchronized on my Windows 7 machine.  It looked like it was configured to sync with DC3, but it was not working.  After some research I found a hotfix,, that fixed it.  I used this command to configure the time synchronization:

w32tm /config / /update /syncfromflags:manual

See for additional settings in the registry.  This KB article is for Windows 2000.  I could not find a KB article for Windows 7, but I think most of these settings still work.  There are other documents from Microsoft about this, but I just liked this KB article best.