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Over the last few days, I have watched the PC as it boots up.
Sometimes it opens a black "Acer" screen and "Press "Del" for set-up" appears for a few seconds at the bottom left of the screen. It then goes to the rainbow screen, I click on the screen or press Enter, it goes to the green log-in screen, the keyboard is active and I put in my password and everything is fine.
Other times, it skips the black "Acer" screen and very quickly opens the rainbow screen. The keyboard is inactive. I have to do a restart, then everything works normally.
Consequently, I don't think that the problem is with the keyboard.
Any more ideas would be welcome.