What should I do if the seller refuses to refund my money after I discovered that the operating system copy I bought from him is intended for distribution only with a new computer, and is it permissible for me to use it with the acceptance of the company's terms, which oblige its return if not purchased with a new computer, and what is the ruling on the work completed on it?

If the manufacturer of a new computer sells it with a disk for its operation and stipulates to the purchaser that he must not sell or donate it to anyone else, or stipulates to whoever obtained the disk without purchasing the device that he must return it and reclaim his money, then this condition is not binding; because it is void and contradicts the essence of the contract, and its owner has the right to sell or donate it to others. And Allah knows best.