Any pc has its recovery procedure ... better it's to buy a SPI programmer to make Firmware Backup and rebuid it !
Anyway there is a procedure fot 3500 model , you can try on 5740 too :
Here is how to recover from a failed BIOS flash update of a Vostro 3500 laptop...
1. Download the Dell BIOS update .exe file to a USB flash drive.
2. Run the .exe file with /writehdrfile parameter
3. Run the .exe file with /writeromfile parameter
4. Copy the .hdr file to winery50.hdr
5. Remove the battery and AC power from the dead computer
6. Insert the flash drive into the dead computer's USB port
7. Hold down the End key and then connect the AC power
8. Dead computer reads USB flash and asks if update should be done
9. Allow the update to finish and then reboot.
10. Computer is now working normally.
Look here too :
https://lazyadmin.nl/it/bios-recovery-de...te-failed/