burning iso to USB drive

My antique Dell Optiplex does not boot from CDROM anymore.  LinuxCNC 2.9.4, which has worked beautifully for many months, is now hanging the PC.  I attempted to use Package Manager to reinstall it.  It fails.  I tried to uninstall it.  It fails, so I guess that I need to reinstall from a USB drive, which is how I installed the now Zombie version.  I do not remember how I burned the ISO to USB drive from Windows.  ImgBurn only burns to CDROM drives.  Rufus does not give me a way to select a USB drive.  Help!

9660. The DVD drive fails BIOS diagnostics. Spindle error. I am ordering a replacement drive. In the meantime, I used a USB DVD drive. The 2.9.2 disk would not boot. But an ancient disk from Sherline called EMC2 did boot and install from that USB DVD drive. This is so ancient that Update Manager does not work. I put 2.9.4 on the DVD. While trying to install, it complained about unmounting media failing. I suspect 2.9.4 ISO lacks the smarts to handle a USB DVD drive. I have successfully installed 2.7.14 before so that is next.