Getting closer to solving my problem.
After some digging I found out that there is hidden "PS\2 compatible mouse" in Device Manager, even though there is only IBM PC AT keyboard connected to PS\2 port(I have single, universal mouse and keyboard ps\2 port on my motherboard). In Device manager it say that device don't work correctly and if I delete it, it reappears after reboot as long as PC AT is connected and disappears after I plug my other keyboard with 5-din to PS\2 adapter(it shows as PS\2 compatible keyboard in DM).
Here is device_ID ACPI\PNP0F03, IRQ 0x0000000C (12) and driver is mouclass.sys that "PS\2 compatible mouse" uses.
Probably because my Asus motherboard has single port for KB and mouse, BIOS sends wrong device_ID to Windows when it reads old AT PS\2 protocol and then Win loads wrong driver. I can't find any PS\2 settings in BIOS, so there is three options to me right now:
1)Change motherboard for one with separate PS\2 ports for KB and mouse. I'll try that option on next weekend.
2)Use PS\2 to USB active adapter\controller. Pricey option.
3)Try force Windows to use correct driver. Desirable option.
So, here is questions:
Can I rename keyboard driver kbdclass.dll and swap it with mouse one or there any other way around to force load correct driver?
I found Aten UC100KMA USB-PS2 controller in store nearby for around 40 USD. It has only few feedbacks on Amazon, does anyone have used it with AT or PS\2 keyboards?