The concept of 'ownership' does not apply with a computer. Anyone who has a user account on a computer can sign in and use the computer, just as if they had purchased it on their own. All your wife needs to use the computer - to 'own' it of you wish - is to create a user account.
Keep in mind that a Windows PC needs to have one Administrator account (no more than one is needed) and any number of user accounts. You can create a new Administrator account for your wife, which she will use to create a regular user account for herself. Then your wife can remove all of your user accounts, if desired, and the computer is exclusively hers to use.
Before removing your user account, be sure to move all your personal files off the computer.