Downloaded latest DOS32A DOS extender. Replaced both stubs again, this time using DOS32A. It works but it has the same problem as with default DOS4/GW extender. The keyboard doesn't work under WinXP. At least, this has proved quite a good exercise for my DOS extenders knowledge. It's good to know that DOS32A supports most of the common DOS extenders out there and that you can "swap" the loader if needed.