Some actions, notably installing the latest help files, required knowledge of which folder OAK is stored in.
OAK is usually located in the directory C:\Program Files\Operis\OAK4, but it might be somewhere else if the defaults suggested were overridden when the product was installed.
The simplest way is to look in the COM add-ins dialog. When OAK is selected, the location is displayed in the dialog.
An alternative is to search your hard drive for the file Operis.OAK.dll and noting which folder it turns up in.
If the file cannot be found on the hard drive, OAK may have been installed on a network drive. You could try searching there.
If you still can't find the OAK4 folder, or the network drives are too large or numerous to search in any reasonable time, another way to find it is to
•invoke the help that comes with OAK (OAK4 | Help)
•drop the control in the top left of the window (click on the icon at the left edge of the title bar, or press Alt+Space)
•choose the Jump to URL... option
•read the address of the folder from the dialog that results.
Tip: The URL will probably be only partly visible, but the concealed part can be exposed by selecting the upper field of the dialog and navigating with the left and right keys or the mouse.
For example, the Current URL mk:@MSITStore:C:\Program%20Files\Operis\OAK4\OAK4_2k3.chm::/chapterwelcometooak.htm shows that OAK has been installed in C:\Program Files\Operis\OAK4.
Tip: The space in "\Program files\" is shown as %20 because the URL is displayed using Percent-encoding. There is a Wikipedia article that describes this coding, but the path can probably be understood without deciphering it exactly.