Your Apple ID was just used to purchase a song from the iTunes Store on a computer or device that had not previously been associated with that Apple ID.

Dear Alex K,

Your Apple ID,
xxxxxxxxx@verizon.net, was just used to purchase "xxxxxx xxxx" by xxxxxxxx from the
iTunes Store on a computer or device that had not previously been associated
with that Apple ID. You may also be receiving this email if you reset your
password since your last purchase.

If you made this purchase, you can
disregard this email. It was only sent to alert you in case you did not make the
purchase yourself.

If you did not make this purchase, we recommend that
you go to iforgot.apple.com to change your password,
then see Apple ID: Security and your Apple
ID for further assistance.

Regards,
Apple

I have been receiving these emails after each iTunes store purchase, But my PC has been associated with my Apple ID and I haven't reset my password, but I did upgrade to windows 10 from windows 8.1 could that be it? and if so how do we fix it?

Regards,

Alex K.