I’ve tried installing the QNX 4.25 June 2011 on desktop Dell Optiplex 380 and it’s ok.
But the keyboard and mouse sometimes freeze and breakdown. I´ve tried to
start the usb driver’s but i’ve receveid the message that the usb “class init- no such file or directory”. If i type usb the message is “no usb controller” . I can’t use the usb keyboard. ?? 
If you can (PC is equipped with PS/2 connectors), it’s better to use PS/2 keyboard and mouse with QNX4 + Photon.
If you can’t (no PS/2 connectors) and you are using only QNX4 (without Photon) or only Photon (and don’t use QNX text console), you may experiment with USB Legacy support Enable/Disable BIOS Setup settings of the PC.
But until now there is no reliable support for USB keyboard and mouse in QNX4 + Photon.