!!
critical HP
Error Code LED flashing Red four times, beeped four times
Power failure (power supply overloaded).
? What Causes This
Wrong voltage selection or inappropriate external power adapter.
✓ How to Fix It
- Verify correct AC voltage setting on rear chassis switch.
- Use HP-recommended power supply adapter for system operation.
Source: page 150 of the official manual
From the manual
This error code appears in:
HP Compaq Pro 6300 SF Desktop