Thank you for your answers. Everything worked out safe and sound: I hooked my HDD as secondary boot device. During the boot process the computer checked in my HDD and it appeared as secondary disk (D:). I could save my piece of work on a flash drive and complete it safely.
Few days ago my PC died with some important files on my HDD I urgently need (for an assignment already overdue!!). Now I couldn't test my HDD for potential malfunctioning but I'm positive it was my mobo and that's not the matter of discussion here.
It was a middle-end custom-built gaming PC...