Bearing in mind that a single DVD will not hold a backup image of your Vista installation, and that computer manufacturers do not include a second hard drive or external backup device specifically for the purpose, do NOT attempt a full system backup until you have purchased extra hardware specifically for the purpose.

System boot drives work hard and are prone to failure because of this. A backup stored on a second partition will be lost in the event that the boot drive fails. This is why manufacturers always suggest that a recovery set is generated from the recovery partition.

Recovery partitions are generally sized around 10gb which is large enough to hold the basic Vista image plus manufacturer stuff such that the computer doesn't flash up low space warnings, and small enough that they do not waste hard drive real estate.

Using second hard drives to store vital backups is not to be advised in that the idea of the creation of a critical backup is based around isolating the backup from anything which could destroy it, i.e away from the stresses and strains of the computer system. The ideal is to have your important stuff on a second hard drive for easy convenient access AND also backed up on an external detachable device.

The best way to store full system backups is on a device which

1. is large enough to store more than two full system backups
2. can be completely isolated from the host computer

Consider purchasing a 'one touch' external backup drive which comes supplied with backup software, or USB hard drive enclosure, suitably large hard drive, and Acronis TrueImage software.

The software that I have seen supplied with 'one touch' devices is generally easy to use but does not allow for much choice, which may be better for the less technical user.