Old windows xp unmountable_boot_volume help!!!!!!!!!!!!!!!!!!!!!

Hello,
My mom wants me to fix her old windows xp computer, but when ever i load it up it says "UNMOUNTABLE_BOOT_VOLUME", and i've read every possible article there is on it. The computer doesn't have a CD/DVD drive in it, so i can't use the xp recovery console from there. So i looked up recover console ISO'S and i've booted any kind i could find with every program that makes a bootable usb, and no matter what, NOTHING FU**ING works. I'm stuck, I've tried booting the recovery console ISO and it either says "OPERATING SYSTEM NOT FOUND" "Disconnect any removable media and restart" or "BOOTMGR MISSING". No matter what i do, nothing works.