I'm pretty sure last time this was asked on here, the best solution recommended was software called Norton Ghost....

I would be interested to know tho, if you took out the HDD from the PC, plugged it into another PC via USB, could you make a complete copy of the entire contents onto an identical HDD, and then put your original HDD back into your PC, leaving you with a complete copy on a spare HDD - so that if the worst happened and your HDD failed or everything went tits up, all you would have to do is turn it off, swap the HDD's and turn it on, and you'd be back up and running in no time?