Thanks Dhon, it worked. I got McAfee software installed, however I have one more problem: Security Center works fine with my account, however there is a problem with all other accounts (including my wife's).
In my wife's account everything loads fine, but when I open Security Center a window opens but it stays blank. I right clicked the icon in the tray to check for updates and all, everything is fine except the window for Security Center that stays blank.
I suspect it might be a problem in Windows because other I tried to open the Account management window from my wife's account and got a blank window also. Again it works fine in my account.
I created a new account for a test, same problem!
Windows XP Media Center SP3,
Thanks for your help, at least my account works and it is secure.
Look forward to some tips if possible,