Oddly enough, I just had this issue occur on my partner's Win8.1 laptop. The following worked perfectly to get his keyboard and mousepad working again:
1- Turn off computer, disconnect the power cord, remove the battery.
2- Press the Power On button for 10 seconds.
3- Replace battery and/or connect power cord.
4- Turn On computer then immediately begin pressing the F2 key repeatedly, about once per second until the UEFI/BIOS screen appears.
5- Press F9 then press Enter (Reloads system defaults)
6- Press F10 then press Enter (Saves the defaults you just reloaded and continues booting)
It can't hurt to try this with a desktop, although you could probably skip the end of Step 1 through Step 3, but even if you follow these exactly, with the exception of removing the battery, it isn't going to hurt.
You will have to double check regarding whether it's F2 or another Function Key on your machine that would throw you into UEFI/BIOS, as the F2 is what's used on Toshiba laptops and the key varies by manufacturer. On my HP it's done by hitting ESC about once per second when the machine is powering up. When the splash screen comes up just before Windows 10 starts loading you should see a "menu" at the bottom regarding which Function Keys can be used during boot, and for what purpose, or just do an online search for your make/model and how to get in to UEFI or BIOS. (It will be UEFI on your machine if it was manufactured at the time Windows 8 debuted or later).
Also make sure that you use F9 to reload system defaults and F10 to save and exit. This will be shown at the bottom of the screen. If your machine uses a different function key to do either of these things then use the appropriate key that matches the noted function.
Edited by britechguy, 09 May 2016 - 06:10 PM.
Brian AKA Bri the Tech Guy (website in my user profile) - Windows 10 Home, 64-Bit, Version 1803, Build 17134
. . . the presumption of innocence, while essential in the legal realm, does not mean the elimination of common sense outside it. The willing suspension of disbelief has its limits, or should.
~ Ruth Marcus, November 10, 2017, in Washington Post article, Bannon is right: It’s no coincidence The Post broke the Moore story