I have a Dell Opitplex 7020 supplied refurbished with two hard drives and running Windows 10. The operating system is on an SSD which sits with velcro on top of the power supply. The machine was running properly.

Yesterday, I installed a Graphics Card. In order to do this I had to move the SSD temporarily whilst fitting the graphics card and then return it to its velcro attachment. On rebooting the machine I had a 'no bootable devices error'.

I reopened the machine and found that only the power supply was attached to the SSD, the main lead was detached and I refitted it. On rebooting the machine I still have a 'no bootable devices error'.

I ran the full diagnostics through the F5 option, this found both hard drives and reported no errors. I went into the BIOS which is Legacy and the boot order sequence is Diskette first, followed by the two hard drives. There is no floppy or DVD drive on the machine.

Is it possible that booting the machine the first time without the SSD attached could have caused this problem? I would appreciate advice on what to do next.