I have my hard drive partitioned into three sections.............
"C" = Operating system and programs (Ghost this partition)
"D" = Personal files, pictures, MP3's, etc. (weekly backup)
"E" = Video files (no backup)
I use an external hard drive to save the Ghost images and backups.
If the OS gets trashed or badly infected with spyware/virus's all I have to do is re-Ghost the C partition. Because my personal files change fairly often I back this up weekly and can easily recover any trashed files without going through a full Ghost operation.
My E partition is used for video editing and encoding............I don't care much if this gets trashed so I don't Ghost or backup this partition.
Partitions make it easy to Ghost or backup as you just grab the whole "drive' rather than picking and choosing individual files. Also, your personal files are less vulnerable being on a different partition than the OS is on.
Also, if you wish...............another advantage is you can run different OS's on different partitions...........just pick which partition you wish to boot from.
Hope this helps...........