2 3 4 is not an error code.
2000:0142 is an error code
2 3 4 Lights on or 2 3 4 beeps are different things.
The computer can emit a series of beeps during start-up if the display cannot show errors or problems. These series of beeps, called beep codes, identify various problems.
Power button light Blue light — Solid blue light indicates
power-on state; blinking blue light indicates sleep state of the computer.
Amber light — Solid amber light when the computer does not start indicates a problem with the system board(CPU) or power supply.
Blinking amber light indicates a problem with the system board or Power Supply and or Addon Cards.
This is likely NOT a mini tower but you did not say which model.
Regulatory Model: D09M Mini Tower.
Regulatory Model : D05D Desktop.
Regulatory Model : D03S Small Form Factor
Regulatory Model : D01U Ultra Small Form Factor.
Regulatory Type: D09M001, D05D001, D03S001 and D01U002
the error means HDD failure (a simple hard cold fact)
the next step is always full and complete HDD tests.
we test it using the great tool called Ubunutu v16+ and newer demo disk or usb stick (free of cost, with free media in hand)
we do that and run the full SMART tests next, or spend all week loading any NEW OS, and failing in 10000s of ways. ok>
do not skip testing hardware or you will be like puppy chasing his tail.
the bath tub life curve on HDD ends about 5 years. old.
so..... there you go on why and how.
also this old, the RTC coin cell battery is due,, we test it 2.9vdc and blow is gone or going bad fast.
7 year life span spec on this cell. ok?