my Acer has 3 usb ports. I believe that two of them are broken and I am worried that if the third also break, I am up the creek, so to speak. can the usb ports be replaced?
If it a laptop then there solider onto the laptop system board. If it a desktop some of them are just wired to the mb and can be replaced. I would check first for bent pins and broken pins on both the devices your plugging in and your pc. If it not a hardware issue it can be a damaged USB driver. Most times updating or installing the mb chipset driver may fix your issue.
Depends on the laptop. Have an Acer Laptop myself, and the two USB ports on the right-hand side of the machine when it's open and facing me are actually connected by a flat ribbon cable. Even if the USB connectors are soldered onto the motherboard, they can be replaced if you are careful and go slowly.
you really need to determine if faulty hardware or corrupt software before next step such as repairs to usb port or uninstall / re install device drivers
Looking into socket with bright light will show if a visible hardware fault with bent pins
Booting from live Linux CD such as Parted Magic and testing usb ports with usb memory stick will confirm problem is Windows drivers or not
Have USB ports been used for charging mobile/smart phones ?
(possible a fuse has blown)