Computer won't boot from USB, won't recognize bootable USB

[The Curious Luddite]

I just bought the Acer Aspire ATC-115-ER41 desktop. It's new and all I did was swap out the original HDD with an SSD I bought. I've tried everything, spent hours on the web and on phone with customer support and I still can't get it to boot from USB to install Windows 7. The USB flash drive is 100% bootable (used Rufus) and functional, as it boots on my other computer and goes through the set up process. Boot device priority is in the correct order. I've tried every single USB port, legacy mode, turned off secure boot, turned on CSM -- although when I do this, the BIOS recognizes the boot devices by their specific names (e.g., "ADATA SX930" instead of simply "Hard Drive"); however, the USB device is uniformly listed as "Removable Device" throughout, which makes me think that the USB is not actually being recognized by the system. All I keep getting is the message, "Reboot and Select proper Boot device or Insert Boot Media in selected Boot device and press a key". Any help, guys?

 

[The Curious Luddite]

Anyone? I tried another USB 2.0 device. No difference. Tried a DVD onto which I burned the ISO image. That won't boot either.