I've installed the Pad Vibration (Pad Vibration Setup.exe) as you suggested. It created a "Game option" shortcut on my desktop.
When I open the devices' control panel, I can see that the Twin USB Joystick icon changed from a joystick to a keyboard. When I open it's properties and check the Hardware tab, I see that there are more entries than before (like HID keyboard device) to a total of 7 entries (USB device, 2x HID keyboard, 2x HID-compliant game controller, 2x HID compatible mouse). The properties for the HID-compliant game controllers remain the same (same date, same version).
After running the setup, I tried to run Resident Evil 3 on ePSXe, but the rumble still doesn't work in the menus (While selecting New/Load game) or while being eaten by zombies. I'm not sure if there is vibration for these situations, but that is what I recall from my childhood.
Just in case, I made sure that the gamepad was
set to DualShock (F5) (shown by the Analog ON window) and the in-game vibration was
set to ON.
If the problem isn't related to the adapter, the driver, or the controller, I can only assume that it is a configuration problem.
This is the window that shows up after I click on Config => Game Pad => Port 1 => Pad 1:
Link to image
As we can see, I didn't touch the Rumble settings for the gamepad, because I'm not sure if I need to or what they should be set to.
Can you help me?