The touchpad on my 5 or 6 year old Acer
aspire 3690-2670 stopped working. I'm using a usb mouse to get by; however, I was wondering if anyone knows of a software or hardware fix for this and how will I know the difference?
The touchpad unit should be available as a part. You could check and see (Device Manager) if the touchpad is still installed or reload the driver, but it's most likely hardware. You could also disassemble the top cover and keyboard to get to the connector for the touchpad and reconnect it, before you replace it.