Windows 7 cant find keyboard

Some keyboards actually don't work with windows 7 you have to make sure it is supported. If these came with the computer then I would contact Acer.
One thing to try would be different USB ports.

try to get in the bios and make sure usb keyboard and usb mouse support are enabled if you have those options

stupidly windows will let you access the bios using a usb keyboard but then not detect it to get into windows

Sorry but lol to the end of the previous post.

can see why you might lol

but its pi**ed me off for years that you can plug in a usb mouse and keyboard and get to the windows log in screen needing to type a password and it wont bloody recognise the mouse and keyboard but if you press f8 or f12 or del or other keys before it hits the start of windows they work and you can browse the bios or boot menu with the keyboard

if you fix a lot of pcs where they forgot to tell you theres a password and you only have a usb keyboard available this can become a royal pain in the ass

wasn't trying to be a jerk just stupid how windows does this