If Windows will not start - perhaps it displays a blue screen or keeps looping around the initial operating system selection menu, or if there is a clicking sound from within the case, then it is likely that your hard disk drive (HDD) has failed.  To prevent any further data loss do not try to start the PC again.  You may have to rely on the backup copies of files you have been taking.

The first step in resolving the problem is to remove the disk from the original PC and mount it in a device that can access it without having to use it to start (boot) the computer.  Data recovery is now attempted to salvage as many of your files as possible.

The manufacturer of the disk is established and a diagnostic tool specific to that manufacturer is run.  This will establish for sure whether the physical disk has failed (as opposed to the file structure on the disk).  If a failure is indicated this may sometimes be repairable, perhaps by mapping the failing part of the disk to an inaccessible file; however, this will usually only provide a working disk for a short time and a replacement should be found.

If the manufacturer specific diagnostic tool does not find an error the disk is then checked for file corruptions (errors of logic) and a repair performed is necessary.  This is a six stage process:

• Partition table

• File structures

• Indices

• Security descriptors

• File data

• Free space allocation

If the disk is repairable then it is usually prudent to replace it with a new on so as to avoid a failure at an inopportune time.  At this stage it is fairly easy to clone an old disk to a new one - even one of different size and make.

If a cloning the disk is not possible then a new drive must be put in the PC and a clean copy of Windows installed.  To do this the recovery CD that came with the PC when new will be used.  Sometimes  PC suppliers minimise the cost of the PC by asking the new owner to make a recovery CD off the hard disk drive, this is the time when you are glad you followed that advice, right ?  If a recovery CD is not available, then it is necessary to buy a new copy of Windows.  Recovery disks are a feature of off-the-shelf PCs, if you were wise enough to buy a custom built PC then any Windows installation CD that matches your licence may be used.