you are right, keyboard and mouse are somehow connected. If I try to change mouse driver, message comes up: "this will also affect keyboard". With standard or MPS Hal, keyboard gets irq 1 and mouse gets irq 12. Furthermore, irq sharing is also present with standard pc hal, although irq 1 and irq 12 are not shared.
I have irq's in standard-pc mode: 1->keyboard, 3-> shared: PCI Expressroot port #3, realtek pcie lan, Intel 8 SMbus Controller 9C22, Intel 8 Series Thermal 9C24, 4-> standard pci to usb enhanced host controller, 5-> UAA Busdriver for HDA, 6-> floppy disk controller, 11 (shared) -> UAA Busdriver for HDA, Intel8 Series Thermal 0A03, Intel 8 USB extensible host controller, PCI Express Root Port #1 and #5.
Now - funny - look at the irq's with mps hal:
1 - shared: Cardreader, keyboard
6 -floppy disk controller
12 - shared: UAA Busdriver, PS/2 mouse
16 - Intel 8 Series Thermal 0A03
80 - USB extensible host controller
108- UAA Busdriver for HDA
112 - shared: PCI Express Root Port #1 and #5
114 - PCI Express Root Port #3
115 - PCI Express Root Port #4
116 - USB Enhanced Host Controller
125 - SATA AHCI Controlller
126 - shared: SMBus Controller, Intel 8 Series Thermal 9C24
So it is definetly a HAL problem.
I found out, that w2k can also be installed in MPS mode on intel i7 haswell notebook, if external usb mouse present and winnt.sif changed to find usb in txtmode setup.