Account Lockout

Is there an account lockout feature with windows xp?
I would like to be able to set the lockout feature to lock
after three attempts to log on, if there is a way for me
to do that. I have been plagued by hackers names appearing
at the top of my web pages, as being logged in. I have
been using the "sign out" link that appears on the same
page in order to sign those users out. These names have
been appearing at the top of the yahoo pages that are
linked to the yahoo messenger, such as, yahoo yellow
pages, yahoo personal adds, etc.
I don't know how to keep these people out of my computer.
Can somebody help?
I have done a complete reinstall of windows, and changed
my password. Still these peoples names keep showing up.
Is there something else I can do to insure my system is
secure? This is a private home, I am the
owner/administrator, and I am using windows xp home
edition. I run zone alarm, and norton antivirus.
Thanks for your expert reply.