As as computer user, you’ve probably heard of the BIOS by now, which stands for Basic Input/Output System.
It is the first software your PC loads so that it can use things like CD drives, mice, and keyboards practically from the moment you turn it on.
But I would guess that you need both the BIOS utility and the BIOS image on the CD.
For, I guess, that you would need the utility you flash the BIOS chip with the image.
It may well be that Dell have produced a BIOS update for that machine to aid it in updating to Win 10, but if you have any doubts then contact Dell to see if they'll give you an answer for what may be a machine out of warranty.
If you do decide to update the BIOS, ensure you have both battery and AC connected because if there's a power blip then you'll brick the machine.