The internal clock on my (very old) Thinkpad laptop is very unstable - it can lose
0.3 sec every 5 minutes for about 1 hour after power-on so not much use asis for WSPR use. To keep in sync with the rest of the world and allow me to use WSPR I use (and would recommend) Karen Kenworthy's program Time Sync (at http://www.karenware.com/powertools/ptsync.asp). This allows me to sync up with a time server automatically as often as every 5 minutes and (differing from an installed sync service) allows me to see how far
I am drifting at every sync point. Also when I don't need it I don't run it.
This program is free (you are also free to donate something) and there are also
other useful free utilities she has written.
Neil