The address shown on whatismyip.com is your external IP address, the one you use on the internet. The other one, most likely 192.168.n.n is your LAN address, which is used just inside your lan.
I have my computer clock automatically sync with the internet server once in a while. That's one of the nice little things I noticed that came with XP.
Lol, well I have done cam "things" a few times. Anywho, I keep it there when not in use since the USB cable isn't long enough to put it next to my monitor.
Note: I noticed the forum time does not change automatically. So if you are in an area where you changed your clocks back, don't forget to change it in your profile. See the pic for info.