New
#31
The OP has a Vista generation computer.You have my sympathy, it's not nice to feel you have been scammed.
If you are very lucky, you may not need to buy a license. If this machine was originally supplied by the OEM with W8, W8,1 or W10 pre-installed, then there will be an OEM key embedded in the bios. You can test if that is the case with ShowKeyPlus.
ShowKeyPlus
If there is an OEM key in the firmware, then a clean install of W10 will read this key and use it to choose the edition to install (Home or Pro) and to activate it with a digital license. If there's no OEM key then I'm afraid you'll have to buy a license.