Dell Inspiron 14z 5423 3 beeps black screen on startup (SOLVED)

My laptop inspiron 14z couldn't start and got 3 beeps and black screen, I had windows 10 installed and Bios A13.

The BIOS update A13 seems to be the problem. With a downgrade to A12 I fixed it. And you need to do that in ms-dos mode cause the bios executable doesn't let you do a downgrade on windows) I first thought that the problem was windows 10 but the computer had the same problem once I installed windows 8.1.

The difficult part was to start the computer again, I followed a youtube tutorial (portugues) to disassemble the laptop and it started, so you can flash the bios. Go youtube and search for inspiron 14z 3 beeps. (notice that in my case the laptop started some times at the 3rd time I pressed the power button, some times I needed more that 20 attempts but finally it booted. You don't need to press any F keys convination or whatever people says, it will eventually start and I don't have explanation for that)

Once in windows make a bootable MS-DOS USB using for example Rufus app. (MSDOS, not FreeDos, I couldn't flash the bios with freedos option) and put the bios in it. BMWZ4A12.exe, can be downloaded from dell website.

Then boot UEFI setup restarting de laptop and press F2 at dell's logo. Maybe you can't access the UEFI when you restart, if you can't, you can access the UEFI using the Recovery setup in windows (search recovery, click recovery setup, go advanced options, troubleshooting, change UEFI settings, restart) go to BOOT section and disable SAFE BOOT option. If you skip this the USB won't boot. Press F10 and restart.

At dell logo press F12 boot menu, and choose USB from LEGACY options. Then the MSDOS will boot. Type BMWZ4A12.exe /forceit press "y" when asked. Wait to the Bios to be flashed. After all this you can go to the UEFI (bios) setup and turn SAFE BOOT on again if wanted (if not you'll see a message on the windows desktop telling you that is disabled)

That's all folks! The laptop works again!