As this might be due to anything, have used "Other"!
Alienware Gaming Laptop, Windows 10, Logitech USB Wireless mouse (with good battery in mouse anyway, but replaced during below actions)
After some use yesterday, but while doing nothing, it suddenly gave the disconnecting USB sound, then the connecting USB sound, which drew my attention.
The Mouse had stopped, but the internal pad worked. Then I discovered that the integral keyboard had also stopped.
Have had this very rarely with other laptops (other Alienware) and as then I went to Device Manager, deleted the keyboard drivers, and rebooted.
This time through the keyboard did not resume working.
I verified latest drivers, latest Windows Update, and did an Alienware systems update.
Then it all worked for the rest of the day (several hours use).
This morning it was back to no mouse, no keyboard.
Reboot via unplugging and replacing the Wireless USB dongle got the mouse back, still no keyboard.
Connected a USB Keyboard and it worked, still no integral keyboard.
Went to device manager and this time used Actions tab, scan for hardware changes.
This brought the integral keyboard back.
Used it for a while, then removed the USB keyboard, still OK.
Hours use later, after a period of no activity but turned on, it was again found to be no mouse, no keyboard.
Rebooted and both working.
Typed this!
Very frustrating, ideas on localising the issue please?
