It usually depends on the end of life of the 'Model' of PC which was returned by the user. If the returned model is approaching end of life soon (in a few months or so), it might be better to mark it as Retired and then ready to be disposed as per the organization's disposal process. If the returned model is not reaching end of life any time soon, it would be better to return it to the stockroom so that it can be redeployed to another user later (Assuming it is in a good working condition). But in both cases, typically the first step might be to return it to the ITAM support team so that they can take the necessary actions (E.g. data back up, data wiping, reimaging, repair if applicable etc.) depending on whether it is going to be retired or redeployed.
Ideally the organization should define the process around PC refresh considering end of life dates, redeployment criteria, retirement and disposal processes etc. Based on the defined criteria, create a new flow by reusing the hardware asset refresh flow mentioned in the following URL and modifying it as per your process and requirements:
https://docs.servicenow.com/bundle/vancouver-it-asset-management/page/product/hardware-asset-managem...
