Gabriele Piscitelli published the complete procedure to enter the service mode of your Samsung SCX-4300 printer, flash it and reset the ink counter. I translated the tutorial in english and I want to share it with you. The original italian article can be found on his blog.

DISCLAIMER: as usual, I am not responsible for any damage you can cause with this procedure!

• First of all, download the software pack: SCX-4300.zip (here’s a local mirror) and extract it in your hard disk (C:\), creating a C:\scx-4300 folder;
• Now fire up a command line window: click Start -> Execute…, type CMD and press enter;
• In the black command line window type cd / and press enter; then type cd scx-4300 and press enter again;
• Type fix4300.exe SCX4300_V1.13_Fact_romdl.hd and press enter; this script will create a new file in the folder, named FIX_SCX4300_V1.13_Fact_romdl.hd. This file is created starting from the unique serial of your printer, and it will replace the original one in your printer flash memory.
• Let’s go to service mode: press the following buttons on your SCX-4300 panel:MENU
  COPIES
  <
  >
  MENU
  >

  You have to execute the entire sequence quickly! If nothing “strange” happens, just press “STOP” and redo it.

• If everything is done, you should see “TECH MODE“ in the display of the printer;
• Press the “MENU” button, follow these steps: DATA SETUP -> FLASH UPGRADE -> LOCAL, then press “OK”;
• Go back to your computer: you’ve to drag and drop the file we created before (FIX_SCX4300_V1.13_Fact_romdl.hd) to the icon named usbprns2.exe;ù
• The display on Samsung SCX-4300 should say:
  - Data receiving
  - Flash erasing
  - Flash Programming
  - Checksumming
  - Download Ok
• Then the printer will reboot. You unlocked it!
• When the printer is ready, just repeat the sequence you used before to enter the “TECH MODE” and follow these steps: DATA SETUP -> CLEAR COUNTERS -> CLEAR ALL CNT. The status LED on the printer should become yellow, then finally green. Now you can print again, using all the remaining ink!