Is someone accessing my computer?

From: rsgrauer (rsgrauer_at_sbcglobal.net)
Date: 09/30/03 

Date: Tue, 30 Sep 2003 12:55:14 -0700

Need some help. In my Security Event Viewer Log I am
getting many Event ID #627's with someone trying to change
passwords to various target accounts. I am also getting ID
#529 with something trying to logon to my computer with an
unkown user name or bad password. This happens every few
seconds. I also have an ID #642 that says my Guest User
account has changed. Is this normal? Doesn't seem like
it. Any help is greatly appreciated.

Ryan