Hi!
This sounds like the same problem I had - I upgraded to Win10 from Win7, and it all worked fine until the first time I restarted. The PC booted straight to the Win10 lock screen, but the mouse and keyboard were not working so I couldn't do anything to actually use the PC. What we think happened is that the first restart must have prompted a bad driver update for the motherboard, rendering all the USB slots (even the USB 2.0/1.1 slots) inactive.
A couple of things to try:
- Does the PC have a PS2 port? If so trying plugging in an old keyboard, or digging out a USB/PS2 adapter (I couldn't do this as I have no PS2 port).
- Does the mouse/kb work okay outside of Windows? Do they work during the POST/BIOS stage? If so, your friend could try starting to safe mode (although this is a pain without mouse/kb as it's meant to be done by restarting from the Start menu while holding Shift or something). I managed to get into the recovery mode by hitting the reset button whilst Windows was starting, prompting it to detect a failed boot. However, every time I tried to go into safe mode I got an error anyway, so this might not solve the problem.
If your friend is experiencing the same problems I had, he could try installing a completely fresh copy of Windows 10. I did this last night and it solved my problem.
1. Download a full ISO copy of Win10 from the FAQ thread.
2. Create a bootable USB using the Rufus tool (also in the thread).
3. Restart the machine and boot from the USB stick. This will allow you to run Windows setup again and format the drive, do a fresh install, etc.
I basically did the above - installed afresh copy of Windows to get the PC up and running and then backed up all my files. Then I ran the set up again, formatted the PC and installed a fresh copy. Since then, everything seems to be running fine, and no mouse or keyboard problems have returned.
Good luck!