I have added a field in the stock record and it will not allow me to delete and gives me an error 'This column contains module data and cannot be removed!'

This error is triggered when you try to delete a standard field, not a Custom one. I have seen this happen before when a field is added to a model than is inherited by another - so if you add a field to product.template, a matching field is added to product.product - and you can't delete the field from product.product (because it is not a custom field) but when you delete the field from product.template, it will delete the second field. I don't have any other advice other than contacting Support if you are a Customer.