Moved this to SecurityCenter 10 - 2010.
You might want to consider contacting Technical Support Chat under Useful Links at the top of this page if all else fails.
First thing that sticks out to me is that you should be using XP SP3 and there is help here with that: https://community.mcafee.com/thread/2007
(Assuming your XP is 32-bit as McAfee is not compatible with 64-bit XP)
Get rid of any beta browsers that you may be testing.
As McAfee uses Internet Explorer for everything regardless of your default browser go into IE and click Tools/Internet Options/Advanced and restore to defaults, if IE8 click Reset, Apply and OK.
Close and reopen the browser and go to Tools/Manage Add-ons and re-enable the add-ons as the above operation disables them.
As you appear to be behind in Windows updates you may want to check that you have the latest Java, Adobe Flash (& Shockwave) Players too.
If there are any older Java or players still listed in Control Panel/Add or Remove Programs they should be uninstalled.
While you are at it you might want to make sure you have all critical & non-critical updates for Windows by using Microsoft Updates as distinct from Windows Update and use the Custom search button.
Use the MCPR removal tool found here to uninstall Mcafee remnants, reboot run Preinstall tool and try to install McAfee again.