I have latest bios (v1.50) but I think there is no way to disable PS/2 port: the options make me choose if I want to use PS/2 for keyboard, or mouse or leave it "auto" (default)

I am talking with windows 7 users that DO NOT USE PS/2 port: can you made this test for me?
Make a system health report (run "perfmon /report" without "")

Does the result reports an error like this?

The device, Standard PS/2 Keyboard, is reporting "tv_ConfigMgrErr24". This device will not be available until the issue is resolved. The Plug and Play ID for this device is ACPI\PNP0303\4-8AB8035-0.

Moreover you can check your device manager for showing hidden device, Do you find a problem in PS/2 Keyboard? (even you have not one plugged in)

If you think I am crazy searching for a stupid problem like this (my keyboard plays good is an USB one) is because I am investigating about system random freeze and I would glad to exclude this cause for example if you say me you have the same error but your system is stable
Sry for my bad english