To make a Product unavailable, go to Store and select the icon Edit this Product to the right of the Product. You can uncheck the Online Store and/or Cashier Store box. The unchecking will remove it from the Store, but any direct links to the Product will stay active.

Direct links to the Product are not deleted when you remove it from the Store by unchecking. Customers will still be able to buy the Product using the direct link if they have been given it.

Products which have already been sold can not be deleted because they have an Accounting record associated with them.

Alternatively, you can Archive the Product. Archiving will automatically remove the Product completely from the Online Store, the Cashier Store, and any Registration Page, as well as pulling it out of any Package, so that it can not be purchased anywhere.