As a matter of clarification, it is not possible to delete any of the runtime folders displayed in the hierarchy panel of the Library. The keyboard delete button has no effect nor will right-click for the contextual menu to bring up the delete command. A runtime folder can only be removed from the Library by selecting the remove Library icon at the upper right-hand corner of the Library window. Usually, through this method, the runtime is retrievable if you know where you placed it initially. However, if you are using conventional content and download folders in Poser's primary folder located in c:/Program Files, expect not to see any content because of UAC protection. Your actual content is stored in a shared location on the drive. Unfortunately, since there are actually 2 Download folders, it is easy to add the wrong folder to the Poser Library.