Installation, PC want's to mount a CD-ROM!!! Why and how please?

Hi Folks, I know it's not really a CNCLinux issue but I am trying to install Debian 10 (linuxcnc 2.8.2 - buster iso) on a Dell Vostro 320 PC, I am using an SD card installed in a USB card reader. When I boot the PC and start the installation, I get to a point where it wants to detect and mount a CD-ROM. As I am not using a CD-ROM , I can't get past this point in the installation, and I don't know how to point it to the USB drive instead! Any help please?
BTW, I have just completed a successful retrofit of a Multicam 140 XYZ Router with a Mesa 7i76 card, I'll post some info shortly.

Cheers S 

Thanks very much, that worked. Unfortunately it looks like the PC has other issues with bad drive sectors. I have my system up and running perfectly with a Raspberry Pi 4 but I want to run Probe Basic and have not found a straight forward description of how to install it on a pi. I get stuck at the section in the tutorial where I have to set the ProbeBasicInstaller file to run as a program, The Buster OS on the Pi doesn't give this option and I haven't been able to launch the program any other way!

Thanks, I'm getting these errors when I run the installer file:
````
pi@linuxcnc:~/probe_basic $ sudo ./ProbeBasic-Installer-py2+3.g231c7ff.run 
./ProbeBasic-Installer-py2+3.g231c7ff.run: 1: ./ProbeBasic-Installer-py2+3.g231c7ff.run: ELF: not found
./ProbeBasic-Installer-py2+3.g231c7ff.run: 2: ./ProbeBasic-Installer-py2+3.g231c7ff.run: @!: not found
./ProbeBasic-Installer-py2+3.g231c7ff.run: 3: ./ProbeBasic-Installer-py2+3.g231c7ff.run: Syntax error: "(" unexpected

````
This is on a Raspberry Pi 4 running all the versions suggested in the installation instructions, and having followed the update and PyQt installs.
 

I am running into the same problem on a Biostar mini-ITX board. But I boot from an SSD (loaded with the linuxcnc 2.8.2 - buster iso). Running live is fine, but when I request installation, it hangs in the same CD-ROM loop. I have no USB to remove, and it did not like unplugging the SSD at all...
Is the current ISO not made for a regular installation?

Elco