|Have you dropped the laptop. or subjected it to some physical jarring, or have you spilled liquid on it, or have you exposed it to liquid such as rain ? |
Those things are the most common events that damage a laptop such that major parts need to be replaced, often the mboard.
An Acer laptop that's about 3 years old that I worked on has a key combo you can press to toggle the Touchpad on /off - Fn and F7 - the F7 key
has a blue graphic of a touchpad with a hand with one finger extended on it - but it sounds like you have other problems.
Using the Tab key should allow you to toggle what is active on the Logon screen, Enter should work fine to select the user, and if you need to type in a password, the keyboard keys should work fine for that.
If your keyboard is damaged, according to the service manual for the model I worked on, a USB keyboard should work fine automatically, unless the USB port doesn't work either.
In the case of that laptop, someone had dropped it. The touchpad and built in display doesn't work, none of the built in keyboard keys work, none of the 3 USB ports work, so a USB keyboard cannot work. There is no setting in the bios that can enable / disable the built in keyboard. It boots fine, a monitor plugged into the VGA port works, but I cannot get past the logon screen without a working keyboard.
If you weren't using a USB mouse the last time Windows fully loaded, you can't move the cursor for it until the desktop screen has loaded and then the USB mouse is recognized. You can get past the Logon screen if the built in or USB keyboard Tab , etc., keys work.