My new Hard disk ( 500 GB - Western Digital)is not detected sometimes by my Pentium IV with HT technology. It has Windows XP OS loaded on it. It was working for about three weeks. Now it is not being detected. My CD and DVD Writer drives are getting detected. Recently I added 1 Gb RAM to make a total of 1.5 GB RAM.
Welcome vkminhas! To be clear, sometimes your hard disk is seen and sometimes it isn't? It's possible that there's something wrong with the power/motherboard cable. Did you install the hard disk yourself? If so, how?
I've also had problems with a hard drive not being detected intermittently, with no other issues (ticking, errors, etc...). Power is probably the #1 culprit in these cases. I put the drive on a different rail, and it worked fine for a while at least. Due to some other issues, I eventually moved the drive to a different system (with a lower watt power supply), and it works fine to this day.
So I would first try switching around which rail it's on (especially if it is sharing a cable with a power hungry graphics card). Double check the data cable of course. Consider buying a quality power supply. And either way, make sure your data is backed up if it really is the drive.