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Here's the strangest thing I have yet to see in 20+ yrs of computer repairs. My in-laws Windowsx XP SP3 has stopped recognizing keyboards. The keyboards work fine in the BIOS, during the boot select process to boot normally, etc. but once Windows comes up it will not recognize any USB keyboard. The USB mouse works fine, have tried different USB ports, different keyboards, etc. nothing works. I can log into the machine via VNC and use the remote keyboard just fine, but not connected locally. Tried a system restore, it says nothing changed.

I am about to just re-install Windows at this point, except I am afraid it will happen again. I have googled for this and it is not unheard of, but I have not found any solution other than nuking it. Anyone have any ideas? I have re-installed the USB drivers for the M/B. Gone into devices and deleted them for a re-install, etc. Keyboard works off a Linux live boot CD, and in the BIOS setup so it is not a hardware issue, and I have tried a few keyboards all of which I know are good and work fine on other systems.

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Have you tried to stick a Windows CD in and do a repair install? – Hand-E-Food Aug 5 '11 at 0:59
The same thing happened to me on a Windows 7 netbook following a Windows Update, except that the computer stopped recognizing USB mice. Uninstalling the updates (including through System Restore) did not fix the problem; I did have to reinstall Windows. – PleaseStand Jun 10 '12 at 10:54
get a cheap usb to ps/2 converter.. – tumchaaditya Jul 11 '12 at 11:15
ps2 converter might resolve the problem but it will be a workaround only. I would suggest changing the USB port to another one. Changing the keyboard, wire, USB socket, adding PCI-Express extension with additional USB ports to test it. If it will not help - uninstall USB drivers - Hi Speed, USB 2.0 and others. Allow windows to install drivers from the network. – mnmnc Dec 14 '12 at 11:43

One thing you can try:

Log in using the username your inlaws use on the machine (if you can), then go into Control Panel and select Keyboard. When the dialog comes up, go to the Hardware tab and make sure under devices there is something listed similar to Standard 101/102-Key or Microsoft Natural PS/2 Keyboard (This may vary some). If it's listed there, see if it shows any errors where it says status down below the device list.

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Very weird behavior. Now I booted it without selecting it on the KVM switch, VNC'd into it and it looked fixed, and sure enough when I switched to it on the KVM it worked fine. I shut it off and left it selected when it restarted, nothing shows in the hardware, the device list shows an unknown USB device. If after I boot I connect a USB keyboard, it will recognize it, but not if I boot with it connected. Does not matter which port it is on either. – Kevin K Mar 16 '10 at 22:44
You didn't mention a KVM switch in the question. Systems can get finicky with those. Try plugging the keyboard directly into the computer and reboot. – fixer1234 Oct 20 '14 at 2:54

I had this problem before. when i brought usb keyboard it didn't work on my pc. it works well on bios, not on boot menu. There is a setting in bios like 'USB Legacy' turn it on.

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