I use Cobian, for backing up my personal Files.
I back it up to a partition, on my 500 GB external harddrive, in an uncompressed state.
I have Cobian set up to keep 3 copies, of my files, on that partition.
When I do a backup, it automatically overwrites the oldest of those 3 backups.
Cobian is easy to set up, and use.
You can set it to backup on a certain date, and time, or you can do it manually, any time you want.
It's easy to set it up to run several different backup tasks, such as backing up different types of files, into their own backup folders, or if there are more than one person using the computer, you can backup each users information into different folders.
Once you have your tasks set up, doing a backup is as easy as, clicking a button.
As far as how often to backup, that depends on how often you add new files, or add something that you can't afford to lose.
Personally, I do file backups every day, but I add a lot of files, and make a lot of changes, in a day.
I agree with the others, about using an external drive.
Harddrives are fairly cheap right now, so I'd get the biggest one you can afford.
If you have an empty drive bay in your computer, available, you could opt for another internal drive, instead of an external.
If you have any problems setting up Cobian, just post your questions in the forums, and I'm sure someone will be able to help you out.
, I also use Acronis True Image
, but I just use it for imaging my OS, and primary drive.
For doing file backups, I prefer Cobian.
I find it easier to use, for that.
It's just a personal thing.