Many people perform daily backups, only to find out (when their hard disk crashes or is corrupted by a virus) that their backup files are useless.
Therefore, it is extremely important to be sure that your backup program is also a restore program (many are not, despite claiming to be), that you back up everything (if you don't you are sure to need the one file that you omitted), and that you have at least one copy of each of your backup files!
Unless over 90% of your drive is used (in which case you really need a larger drive), drive imaging programs are far too slow and inefficient (compared to file backup programs). Similarly, if you have any amount of files, backing up to CD-ROM or DVD takes too long to be practical. And, the longer a backup takes, the less likely you are to do one daily (which is essential)!
I have three computers networked. Each of them are partitioned as follows: C=Operating System and Program Files, D=Data Files; E=Downloaded program files and Windoze Patch files; F=Backups.
I use Beyond Compare to synchronize the data files between computers over the network. Thus critical data is duplicated on at least two separate computers. This is my first level of protection.
Then, using the backup program supplied with Windoze, I backup each computer to its "F:" partition daily. And incremental backup (of changed files) is done daily. Once a week, a "full system backup" (of everything except the F: partition) is done. This is the second level of protection.
Then, to protect against possible loss of the backup files, a copy of the nightly backups is made to a removable hard drive, which is stored in a fireproof safe.
This not only allows me to restore my computer (to its status as of the previous evening) in case of crash, virus, or regretable program installation, it allows me to go back 3-4 weeks (in case I don't discover a problem for some time)!
My backup procedures are scripted, and take about 5 minutes each night, and less than 30 minutes for the weekly full system backup --- far less time than ghosting or writing CD-R's.