WIN XP - check who's logged on PC

Sometimes when I have to restart (ex. after Windows Update, but not only after this), I get a message that 'other people are logged on & restarting will...'.
I have other computers hooked up into what I guess you geeks call a network (a router/hub thingie with too many cables), but no one is using them. They stay on just about all the time. I have cable ISP.
I don't get the message at every restart.
How can I check to see who or what is logged on?
Whenever I get the message, I just figure screw 'em & restart anyway. So far no harm that I can tell.
Thanks -

 

You must use fast user switching. This is a feature of XP that allows you to switch between users without logging off and closing their applications. It has nothing to do with your network. Its all about the local machine. You can disable it by doing the following:

1. Open Control Panel
2. Double-Click 'User Accounts'
3. Click the link that says 'Change The Way Users Log On and Off'
4. Uncheck the box next to 'Use Fast Switching'
5. Apply your settings.

This will prevent the message that other users are logged on, because they will need to log you off to log on!

 

Thanks for the help.
Just myself and one other user listed, Guest is turned off.
I unchecked the Fast User Switching.
We'll see if I get the message again sometime.
It's kinda funny though, because we both (users) are in the habit of logging off when finished and there hasn't been any indication that anyone else is logged on.
We keep XP set up so that the User screen with the little profile pictures is visible and sometimes I notice that there will be a message under the username if something is running.
Anyway, thanks again for the help.
BTW - is there somewhere that will indicate if an outside source is accessing my computer?

 

Sorry for the delayed 'thanks'.
I already use ZA. I don't remember seeing anything showing active users, maybe I overlooked it. I do recall an active program indicator and the alert log.
I'll take another lookie-see.
Thanks.