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quite frankly if you are trying to put win 10 on a computer that originally came with XP it may not be fully compatible. If asked i would have recommended against it. There are some major bios issues because win 10 wants a uefi compatible bios and that was not available when XP was sold. Also most xp era computers will run very slow on win 10 even if they can handle it.
You can check the compatibility on this website
If you did a CLEAN install by wiping everything off and reformatting the drive and you get security issues i would suggest doing it one more time and make sure that you pick the option to use a microsoft email address as your login ID. MS programs expect that when they see win 8 or 10. The windows 8 or 10 login with the ms email address is what grants your rights to all the ms programs that were registered under that email address.
If you want to try that it might work. If you want to return the win 10 that would probably save you a lot of hassles going forward until you can purchase a computer designed for win 10. You need to contact the people that you purchased it from to get a refund however.