KB / Mouse work in bios but not while installing windows

I have an ECS nForce4 A939 mobo with a64 3200, 1gb corsair ram, pci-ex
gfx, 120 gig ide hdd, atx2 power supply, dvd-rw.

I can use the keyboard / mouse (which are ps2) in bios setup etc, but
as soon as i load the windows installer it gets to the blue screen
asking to install or repair and then the kb/mouse stops working.

Never seen this before!
figured faulty mobo or dodgy bios , so i would flash the bios - but
when loading a boot CD made in nero, it reboots. so faulty ps2 ports?
no probs i'll buy usb kb/mouse!

to no effect, same result.

I installed windows on another base unit with this hdd and it loads now
on the computer but no mouse / kb when getting into windows.

Default bios loaded atm, any ideas anyone?

Thanks!

mooneh