I've just been reading Ray's newsletter issue #32-2 about File backups vs. Disk Image clones
Ray and dlwolff0 have got it dead right and I also do this, trouble is it takes ages but has got me out of big trouble several times.
I use Norton Ghost (my favourite) and Acronis Disk Image and they are both good.
In order to reduce the time to do backup/clone you might like to try this method with Norton Ghost.
Firstly don't run Ghost in Windows - create the boot disks as appropriate to you system and run Ghost from them
Secondly hardisks are now so cheap clone your C drive to another Harddisk
Thirdly - to speed things up take the IDE cable off your cd/dvd drive and fix it to your new hard drive (your computer thinks it's now a cd/dvd disk)

Doing it this way will cut time taken from (in my case) twelve hours to just two hours.
and when your box goes wrong simply whip out the old drive put in the new and away you go and that takes all of ten minutes but as dlwolff0 says your cloned disk is only as good as the last time you cloned it and is not a replacement for everyday backups