Computer beeping

Hello, I am having serious trouble with my computer. It keeps freezing randomly, sometimes it freezes onwindows log on, sometimes it doesn't freeze at all,sometimes it freezes even before windows loads. Nothing works, no keys work at all it just hangs and then shuts down automatically after few mints and then starts again automatically after few minutes. Ihave scaned disk no bad sectors or any problem found, I did memory diagnosis too and it was fine, scanned for virus and no virus found. Checked if my processor is overheating but all temperatures are down to 40c. I have even installed new windows and deleted all unnecessary softwares. I have checked device manager and no driver issue there. It was working this morning but now it is not even starting. Whenever I switch it on it starts beeping. It beeps thrice in an endless loop. Please can someone tell me what is the problem with it?

Pc specs: Intel core i3-3210 cpu @ 3.20ghz 2.00 GB ram 32-bit operating system windows 7 Intel desktop board Dh61ww Powersupply evermax noisetaker model eg375ax-ve