I loved TP4- especially the "Edit with Textpad" feature available in Windows Explorer's context menu. Very handy for quickly inspecting any filetype not associated with TP. After installing TP5 on a new machine, the context menu entry is gone
Go to Configure -> Preferences -> General, and look towards the bottom of the dialog box "Put Shortcuts to TextPad on" section, and place a tick in the box labelled Context Menu.