PC gives long beeps and input devices disabled! - Please help

I am facing a strange problem from yesterday. I have an Asus A7N266VM SE motherboard(5+ years old) and an AMD Athlon XP 2400+ processor. When the PC was running yesterday, there was a continuous long beep(around 20 sec). When the beep was being heard, the keyboard and mouse stopped working and after those 20 seconds, they started working again. I was web surfing at that time and the computer did not reboot or shut down. It sounded the alarm and after that I could work in peace. But after another 30 mins,the beep sounded again and again the keyboard and mouse stopped working. This beep has sounded more than 6-7 times yesterday and the same thing was repeated.

Today when I started my PC in the morning, I saw that my keyboard is totally disabled during bootup due to which I am not even able to enter the BIOS. It booted fine into windows but neither the mouse nor the keyboard is working. I can see all the icons and everything but the mouse pointer remains fixed at one point and there is no response when I press the Windows button on the keyboard. I used a live CD of Ubuntu 6.10 next. It booted up fine and I could see the desktop but here also the mouse and keyboard is not working. I removed the RAM and cleaned it(as I do not know what else to do) but the problem persists.

What is wrong?

Update: My motherboard runs on Award BIOS.
I am also hearing a faint tik-tik sound during bootup i.e when the computer starts and during the time the Windows Boot Manager is displayed(I have two Win XP's) for 30 seconds. After Windows starts booting, the sound disappears. This happens also when I use the Live CD of Ubuntu. 30 sec is given to choose what I want to do with the Live CD. After that it starts to boot and the sound disappears.

I am not sure from where the sound is coming, whether it is the HDD or PSU or processor fan.

The beeps might be due to the RAM stick being loose. Check that. And that noise that you are describing is mostly from the HDD. Since you are saying that your Keyboard is disabled during boot, I think, the BIOS is having problems initializing devices after a certain point. Try disconnecting your HDD and see if you’re able to access the BIOS. The problem is mostly to do with the HDD. It’s time you get a new one, even if it works.