I am really sorry to say this, but this is a scam. There is no way that Microsoft could tell remotely that something is the matter with your computer. This has been flagged up on here several times before - if they rang you, they are fishing for your money.
Get off the computer and on the phone now, and cancel that card you used to make the payment - your card reporting line will be open 24 hours.
If anyone rings you, it's unsolicited, never give anyone any money unless YOU have asked them to do it.