Hazelnut a good question to pose these days with all the weird things out there that can take a system down, apart from the user making a MAJOR mistake, as I did many years ago. So since then I have gone "overboard".
As previously stated I use "Allway Sync" to a 500gig USB HD for Data, I also use "Lacie Backup" for drive "C" (SW came free when I purchased an expensive Canon Laser printer / scanner / copier / fax machine. It also shipped with a Rebate for a SATA 500gig HD).
Now come the most important part, my PC is equipped with 11 bays, 5 for Hard drives + others, so I run 5 SATA HD's plus the USB 500gig HD, some 1.7TB of storage. So when I back up my System drive "C" with "Lacie" it backs up to a "separate" physical HD. For the last 6 years my standard build for me and my after hours clients always includes a min. of 2 physical HD's. If not, I do not build the box.
For my 5 PC's on my network I uses all Gigabyte motherboards as they all ship with (well the ones I purchased) "Xpress Recovery2" software which is a utility that allows you to quickly compress and backup you system data and perform restoration of it. Supports NTFS, FAT32 & FAT16 file systems, Xpress Recover2 can backup data on PATA and SATA hard drives and restore it.
Xpress Recovery2 can only backup and restore the first physical hard drive that has the operating system installed. You boot from the Gigabyte CD that comes with the MB to run the Xpress Recovery2 system to backup and restore. By the way it takes longer to backup than restore.
Not supported (no issue for me) OS requirements are Win XP SP1 or later, USB hard drives (can not store the backup image on them) Hard drives in RAID/AHCI mode.
I also like you create a new backup every month like clockwork only because I created a MAJOR mistake many years ago and the heartache and time it took to rebuild and restore my data from "hard copy" I do not wish to repeat the exercise.
I really need to get a life as I also use Ghost and create an backup image (every 6 months) which is stored on another HD, a different PC across my LAN. Data only backups are made weekly, data Allway Sync is performed every time I shut down, this is done automatically.
Sorry to be so long winded about the subject, BUT backups are so important, and if one does backup, one should do it regularly (at least monthly) as you suggest Hazelnut.