|First of all you need to protect your irreplaceable personal files by keeping at least TWO copies of them in separate places. If the files are extremely important you may want to keep more than two copies. I have my photos burned to DVDR in addition to residing on internal and external hard drives. My external drives are not running all the time. I isolate them when not in use.|
Even if you have original media for your OS and all your programs imaging an entire partition can save you literally hours of time to re-install if you have cause to to do.
If you think about what is required to re-install everything you have on your computer, plus customize all the settings, you are easily talking about tens of hours.
The major difference in simply copying files and imaging a partition is that the image is compressed to save slack space.
For items that you may need to access quickly, copying is a better choice because you don't need to unpack those files in some manner.
The reason it is recommended you save a previous backup is twofold. Once you start to overwrite a previous backup you have destroyed it. If creating a new backup should fail for any reason or should prove to be un-restorable at least you have the previous, which may not have the most recent changes but is better than nothing.
With the price of storage space being so cheap there is reason you can't have enough space for multiple backup/images.
One thing to note. Music and photo files are already in a compressed mode by their nature so including them in an image does little to save drive space. That is a good reason to use multiple partitions. Simply copying those items makes them instantly accessible. Your Operating System (Windows) is what changes weekly if you use auto updates. So it makes sens to back up the partition with Windows on it the most often. Conversely, your installed programs rarely change, so the backup frequency can be much less often.
I use 3 partitions for the above reasons. C: holds Windows and a few key programs. D: Holds my installed programs. E: is used to store music, photos, created files, etc.
Hope this long response helps.