Problem with u-boot file in beagleboneblack

I have bbb by mistake i moved the file u-boot.img out of the device (it is now in the desktop of my computer ) and if i want to return it, i recieve a message that says the disk have write proteccion

Did you actually "move" the file (create a copy on your host computer
and DELETED from the BBB)? Or just create a copy?

  How are you trying to "return" it? Note that Windows (if that is the
host system) does not understand Linux EXTn partitions, so accessing a BBB
SD card won't work.

  Does the BBB boot? If it does, you will likely need to sftp the file
into the USER directory, then ssh into the device and use "sudo mv ..." to
move the file from the user directory into the system protected directory.

I actually copied the file to my desktop and then I deleted it from the bbb, now I have that file but when I try to move it the legend appears, the disk is write-protected.

I am trying to return it by dragging the file from the desktop onto what is recognized by my usb port.

the beaglebone does not start, nor is it recognized by my computer unless I turn it on with an SD by pressing the boot button, I am really a beginner with the bbb.

I don't know if you know of a way to reset the factory beaglebone.

I actually copied the file to my desktop and then I deleted it from
the bbb, now I have that file but when I try to move it the legend
appears, the disk is write-protected.

I am trying to return it by dragging the file from the desktop onto
what is recognized by my usb port.

  If you mean that "BeagleBone Getting Started" thing -- that isn't even
a real disk device. It is just a read-only /file/ mounted to look like a
file-system.

  Do you have a copy of PuTTY installed on your (presume Windows)
desktop? https://www.putty.org/ It includes an SFTP client for file
transfers (though FileZilla and WinSCP provide something closer to
drag&drop. PuTTY is command line -- and if you want to work with Linux
systems, you MUST become comfortable with using command line tools, not
drag&drop graphics).

the beaglebone does not start, nor is it recognized by my computer
unless I turn it on with an SD by pressing the boot button, I am
really a beginner with the bbb.

  I'm not surprised -- the file you deleted is part of the boot-loader.

I don't know if you know of a way to reset the factory beaglebone.

  The quickest solution will likely be to download the correct flasher
image from Latest Software Images - BeagleBoard burn it to a 4+GB SD card,
and let it reflash the eMMC image. Warning -- that degree of reflashing
results in a power-draw: you need to use a 5V power supply on the barrel
connector of the BBB, NOT rely on USB power.

  The other would be to boot an SD card, MOUNT the eMMC somewhere on the
filesystem, SFTP the file to the user directory on the SD card, then "sudo
mv ..." the file from user directory to the correct directory of the
mounted eMMC.

  If the device hadn't been updated to Debian Buster (v10), the first
solution is highly recommended.

Exactly I mean the BeagleBone Getting Started, since I moved that file it stopped working

I have putty installed, before I can connect via SSH connection using root user and root password, it currently tells me that the password is incorrect.

as i select the correct flasher because i have installed several and the problem continues

I have putty installed, before I can connect via SSH connection using
root user and root password, it currently tells me that the password
is incorrect.

  Standard practice is that log-in to root is not allowed, and root does
not have a password. You are supposed to use the defined USER login
(debian) and USER password (temppwd), after which you use "sudo" to run
privileged commands.

as i select the correct flasher because i have installed several and
the problem continues

  If you've properly run a flasher image, it should have rewritten the
entire eMMC with a valid OS.

It sounds like you are not even running putty or putty closes after you select /dev/ttyUSB1.
If you are running putty in linux ubuntu, you must open a terminal in ubuntu and run putty as sudo “$ sudo putty” because you are trying to access a device in /dev.

Regards,
Ray