i just reinstalled windows and didn't install the "windows file sharing" part... could that be the reason my usb drives don't recognize my external hard drive now?
Your usb drives? If you're saying that your USB ports can't seem to recognize your external hard drive, then you may have to install your motherboard's drivers. Check the install disc that came with it.
might want to make sure your external drive is turned on too But yea, if you reinstalled Windows, make sure motherboard drivers are also installed. just in case.