This attempts to help answer the question, which files should I backup and how ?

The answer is different for most people as each have their own tolerance to risk and loss of data.  There is a scale of activity - at one end of the scale, the vast majority of people do not take backups at all, this incurs no time, inconvenience or immediate expense and keeps data recovery technicians in business.  At the other end of the scale, by example, when I was responsible for the databases on which the Yellow Page directories of the East coast of America were based, I had to be able to recover several terabytes of data in a very short time, so I took three independent types of backup (logical, physical, image), on different media each day, and these were sent off site to a fire and bomb proof safe.

What to copy.  Typically it is only necessary to backup files which are not already held elsewhere.  So as long as the installation disks, product keys and personalised settings for an application are available there is no need to take copies of that application.  Data files, however, should be backed up as often as the maximum amount of time the owner can bear loss of the data.  So the more frequently data is changed, and the more important the data, the more frequently it should be backed up.  There is a separate page explaining how to back up Outlook Express files.

Disaster recovery tests.  There is little point in backing up data unless it is recoverable in the event of loss or corruption, so periodically it is worth proving that the data can be brought back and used in the application.  This is especially true after the application has been updated, or hardware upgraded.

The medium used to contain the backed up data should be different from the original source if possible as sometimes the entire disk goes bad.   Fire, flood or theft will not affect data held well enough away from the computer.

·           At about £35 for a 20GB hard disk, a second drive is often the easiest way to provide an alternate location and, if fitted internally, it can double up as space for temporary storage to improve overall performance.  Smaller 2.5inch external disks can often be powered from the USB port and are a compromise between the speed and price of the larger 3.5inch  disks and the following smaller media.

·           If several computers need to be backed up an external (Zip, Jazz etc) disk may be practical.  USB pen/thumb drives are popular and commonly hold 4GB or 8GB now. They are small and convenient but not suitable for large media collections.

·           If two or more computers are connected in a local area network then another computer may house copies. 

·           There are Internet sites (such as RBack) which hold backups for a fee - this is usually secure but you need to be sure of access in the event of a disaster. There are also free options as mentioned on my Blog.  

·           DVD drives are common now, and data greater than 4.7GB (9.4GB if dual layer) can be spanned over multiple disks.  BluRay disks will hold 25GB per layer but the cost is high. 

·           CD burners are similarly good for about 700MB

·           floppy disks (1.4MB) or USB memory sticks can take easily portable copies.

Which program to use for backup.  The application used to backup data must be available at recovery time i.e. held somewhere other than the hard disk it will be used to recover from !  Microsoft’s Backup program is universally available, free and good for all but the most demanding users.  Failing that, third party solutions are available which offer more bells, whistles and expense.  Personally, I use Acronis True Image for my weekly and monthly backups, and for the really important and frequently changing files, I run Microsoft's SyncToy to echo changes to a second internal disk on a 24 hourly schedule.

The simplest way to copy data is the COPY command; however it does not compress data, and so is often only suitable for already compressed files (.JPG, .MP3, .WMA, .ZIP etc.)  Programs designed for file bundling are often a good compromise between cost and ease of use - WinZIP and RAR are the most popular.

Types of backup.

All files have attributes, and one attribute is designed to flag whether the file has been modified since it was last backed up.  In Windows this can be seen by adding the attributes column in Windows Explorer (right click the column title), or in the file properties, (Advanced… button in XP).  If the Archive bit is set (i.e. visible as an ‘A’) then the file has not been backed up since last modification.  This can be used to determine which files qualify for backup so as to avoid wasting time and space backing up files more than once.

·           Normal (partial or full).  Backs up all selected files and clears the archive bit for each file, indicating that the file has been backed up.  Normal backups give you the ability to restore files quickly because files on the last destination medium are the most current.

·           Copy.  Copies all selected files but does not clear the archive bit for each file, indicating that the file has not been backed up.  Copying is useful if you want to back up files on a different backup medium between normal and incremental backups, because copying will not invalidate these other backup operations.

·           Differential.  Backs up those files created or changed since the last normal (or incremental) backup.  It does not clear the archive bit for each file, indicating that the file has not been backed up.

·           Incremental.  Backs up only those files created or changed since the last normal (or incremental) backup.  It clears the archive bit for each file, indicating that the file has been backed up.

·           Daily.  Backs up all selected files that have been modified the day the daily backup is performed.

Windows XP.  Microsoft do not include the Backup program by default in XP Home Edition, but it is available for installation.  Locate the installation CD and right click on
<your CD drive>:\VALUEADD\MSFT\NTBACKUP\NTBACKUP.MSI
Then pick the Install option.  Backup will appear under the System Tools | Accessories menu.  Note however that Automated System Recovery is only of use to XP Professional users, in the Home edition the functionality appears to work, but there is no way to restore using it !  Also, it will not backup directly to a CD device, you have to go via a disk file.

Boot Disk.  Finally, remember to have a means to start the computer if the hard disk fails due to hardware problem, software corruption or virus attack.  Enable System Restore, backup WMP licences and privacy keys, create a password backup file and keep 1ComputerCare’s number stuck underneath the keyboard.  An image backup can be included in the fixed price maintenance service performed by 1ComputerCare.  Remember: bad stuff does happen, and not just to other people !