Depends on the BIOS, and somewhat possibly the board brand. For an AMIBIOS, 3 beeps means 64K base RAM failure. For Award, it means video or memory failure (Award provides very few beep codes, and they all apply to memory or video). Phoenix BIOS apparently uses groups of several beeps, like 2 beeps then 3 beeps 1 beep 4 beeps, which yours doesn't seem to be so I assume you have another BIOS type.
Try pulling out memory modules and trying them one at a time. Try resetting the CMOS via jumper or pulling out the battery. Make sure the heatsink is properly mounted (not reversed) and that the fan is plugged in to the right header on the motherboard. Unplug everything leavinly only CPU and memory, see if it beeps without the video card. See if it beeps without the memory installed. Make sure nothing is touching the case metal that might be grounding it.