I want to clone my HDD for backup, to another HDD. I am thinking of using a USB external HDD to do this. I want this drive to be bootable, so if my HDD goes bad all I have to do is exchange the drives. You think this would be possible due to activation ETS. Also thinking that my system should be upgraded as much as possible, that is as much as I can afford before I do this. 

Custom Build, MICRO-STAR , AMD 64 3000 @ 1.8 GHz, 2,559 MB PC3200 @400 MHz RAM, 160 GB HDD, NVIDIA GeFORCE 6200 Turbo Cache PCIe with 256 MB RAM, Windows Vista RC1, (Rating 2.7)