PC power ON problems

1.
You turn on your computer and there's nothing and you hear repeated loud beeps!

What it means :: Hardware trouble you probably need to replace something

Description :The beeps you hear are called beep codes and they are usually associated with a malfunctioning hardware.The type of beep signifies the type of hardware that had failed (cool isn't it?)

Now its not as simple as that, different BIOS have different beep codes ,the two most popular BIOS are AMI and Phoenix.

Their respective beep code info can be found here http://www.webopedia.com/quick_ref/BIOSBeepCodes.asp

Solution:Once you identified the correct interpretation of the code you will know what is gone faulty and you can replace that hardware, most often its the RAM or Video system failure.

2.
PC gets stuck at the Windows loading screen and there seems to be no hard disk activity (the hard disk read/write light does not flicker)
(Or)The Computer powers on and you see the OS choices menu (if you have more than 1 OS) but gets stuck when you select something
(Or) The Computer powers on and you get a black screen in windows XP

Description :

PC powers on but when I choose an OS it goes into a black screen and there is no hard disk activityTried reinstalling windows, restoring system. This baffled me for quite a while.

What it means :: Hard disk trouble a reformat would help

Solution :

Format the hard disk partition where you have the OS.Reinstall windows and run a good Virus scanner on the rest of the partitions.
CAUTION: Removing or reformatting a partition will delete all of the data that exists on that partition.