Q.. Why does a computer manufacturer ask you to make a backup of the system when you start your computer for the first time?
A. Because hard drives are not as reliable as they could be, and even new ones can break. The manufacturer recovery partition is only good if the hard drive is still in working order.
The above backup will only be good on the day. Anything that you add to the installation, hardware or software will not be included, so you should make another backup in time which better reflects your computer as you want it for normal daily duties. Every time that you add anything major, remake the backup..
Limitations of the above.. OK.. the above covers a major crash. A full system backup will wipe out anything on the drive that was added after the backup was made, just as the manufacturer recovery process will.
You need to make backups for the files which you create or download. Included in these backups would be music, photos, email, program installation files that have been downloaded, for the times when you accidentally delete a folder or for when the full system backup does not contain everything to the present time.
The best way for a home user to back up these files is to do a straight burn onto a CD/DVD or to copy the files to suitably sized flash or external hard drive. This will make them available to any computer, any configuration. If done this way, recovery of the files is NOT reliant upon a backup utility which may not run or be compatible with the OS to which the files are being restored.