This code may indicate a malfunctioning timer 1, or failure in the first 64k of RAM memory. Turn off the computer, reset any loose chips and retest. If the beep error persists, you can try testing the motherboard with known-good memory from a compatible computer. Replace the first 64k of memory (the single row of chips in a XT clone, two row chips in a 256-based computer, and from one to four rows of chips in a 386 or 486 computer). If you still receive the four-beep error, replaced the motherboard.