Although the time on my computers has always been correct, it appears many people have not been so fortunate. Ed Bott has posted instructions on How to fix Internet time sync. Like others, he has apparently not had success with the clock synchronized with time.windows.com and changes the location to one of the U.S. government servers.
With Windows Vista, it is easy to access Date and Time. Just click Start (the Vista Orb) and start typing "date and time". You will find it the second selection after typnig "da".