PowerPoint includes a Recently Used Files List that displays the presentations you have previously opened. The default number of presentations displayed is four. If a presentation is no longer available, but still appears on the list of recently used files, you may want to purge the list to clear it.
Unfortunately, to clear this list, you have to disable the recently used files list and then re-enable it. Within PowerPoint, click Options from the Tools menu. From the General tab, clear the check beside the Recently used file list option and click OK. This step will purge the list. Now you need to re-enable this feature by repeating the steps just listed. This time make sure a check appears beside the Recently used file list and click OK.
All the presentations that previously appeared in the list will no longer be there.