I've tried uninstalling ZDelete but references to ZDelete still appear.

When uninstalling the software, you should immediately restart Windows to finish the uninstall.

If ZDelete still appears, there is a method to manually remove any ZDelete reference although you should be careful and take some precautions before you tamper with the Windows Registry.

CAUTION: We cannot be responsible for any lost of information or any loss of data as a result of actions taken. Please tread cautiously and use at your own risk. Please review the following document on how to use/edit/backup the Windows registry before you attempt to make any changes. How to back up and restore the registry in Windows

Once you have run regedit, select My Computer and from the menu bar select Edit and then Find. In the Find What field, type in "ZDelete" (without the quotes). Then press the "Find Next" button. A few instances may be found. When an entry is found, press the Delete key on the keyboard to delete the item. Close the regedit program and restart Windows. Once Windows has restarted, you will notice that ZDelete is no longer there.