text: After an uninstall, Salesforce automatically creates an export file containing the package data, associated notes, and any attachments. When the uninstall is complete, Salesforce sends an email containing a link to the export file to the user performing the uninstall. The export file and related notes and attachments are listed below the list of installed packages. We recommend storing the file elsewhere because it’s available for only two days after the uninstall completes, then it's deleted from the server.
  If you’re uninstalling a package that includes a custom object, all components on that custom object are also deleted. Deleted items include custom fields, validation rules, s-controls, custom buttons and links, workflow rules, and approval processes.
  When an installed package includes any component on a standard object that another component references, Salesforce prevents you from uninstalling the package. An example is a package that includes a custom user field with a workflow rule that gets triggered when the value of that field is a specific value. Uninstalling the package would prevent your workflow from working.