Configure hardware → Set UPDD v4 directory
The Universal Pointer Device Driver (UPDD) from Touch-Base, version 4, requires that any software using it (such as Whisker) changes to the UPDD installation directory (where tbupdd.ini) is located prior to initializing the UPDD interface. This is curious, since UPDD could and should do this for itself. As it doesn't, Whisker needs to know where UPDD is installed (by default, this is C:\Program Files\UPDD).
By default, Whisker reads UPDD's location from UPDD's section of the Windows registry (HKEY_LOCAL_MACHINE\SOFTWARE\Touch-Base\InstallDir). You can override this behaviour here, though you shouldn't need to.
This option is irrelevant for earlier versions of UPDD.