Winxp Security Center

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When I attempt to turn on the built in firewalll in Winxp Home I get a
messsage stating that it cannot be turned on. I have run ad aware and
spypot plus avast virus checker and all is clear. There is no security
center in any file on the computer. Automatic updates and virus
protection are on. How can I correct this without getting a separate
firewall off the internet. Thank in advance for any help. John
.