If you used the card to buy your current computer and monitor then they are using your card as a reference only. They can't charge you again for what you have unless they want to be investigated for fraud. Most CC's anymore will work with you in case of disputes on billing...all of mine do as I had somebody use my debit card info in Kissimmee, Fl. a week ago that they obviously stole my info from a vendor I used. No problem...I have alerts on my account that lets me know anytime my card is used and when I got the charge I called my bank,,they put out in investigation on the charge,,credited back the amount on my account and issued me another card...easy and 5 minutes later alls well the with the world.
The smart consumer will do this...ensure that you set up your account that will let you know everytime your account is charged for anything that way you aren't waiting til the end of the month to see your charges. Give the company your info and you'll be fine..worse case scenario is HP uses your card fraudulently and you report them and you get another card the next day and all your money back.