I've been using "About Time" for so long I could hardly remember where I got it, it's;
http://www.arachnoid.com
and its written by Paul Lutus who calls it "Careware". Nice guy.
Its a tiny process running in the background which synchronises the windows clock to an Observatory clock of your choosing when you're on-line. The Bios clock is synchronised in turn and the system remembers the time on shut-down. It works on a network, too, as you can specify the workstations to synchronise with a Server or master station, even when off-line.
Having said that, if your PC clock is more than about 1 second out in a month, there is something wrong. You might complain under the warranty.
[Edited to fix the link]
[This message has been edited by fobotcso (edited 13 February 2001).]