Go to the folder where the firmware was downloaded using 'cd'. For example, make a simple folder (C:/ Firmware) ; now type in 'cd c:/firmware' .
Input the following command to send the bootloader: 'copy filename.bs LPT1', where the filename is 'BOOTXE99_1204' and 'bs' is the extension. 'LPT1' is the parallel port.
After the bootloader is succesfully sent, input the following command for the firmware upgrade: 'copy filename.zg LPT1' > filename is for example: '4212HE10_12071' and 'zg' is the extension.
There must be a space between copy and filename.zg ,as well as between filename.zg and LPT1, otherwise the command will give an error. The command should look like copy^filename.zg^LPT1, where '^' indicates the space.
Now the firmware should upgrade slowly
Follow the steps above until the latest firmware is installed. If the printer refuses in any way to upgrade the firmware, power up the printer and hold the 'Pause' and 'Test' button. It should display a message that contains 'Boot Mode'. Try one more time to upgrade the firmware via 'Boot Mode'.