Well if you're sending it to someone, it'd be a good idea to ask what tools would be handy for him.
Otherwise, if you can boot from a CD, I highly recommend Clonezilla, which is free and open-source and can backup both to images as well as clone drives: http://clonezilla.sourceforge.net/
Failing that, you can find an old copy of Norton (or even pre-Norton) Ghost, which can fit on a single 3.5" floppy. Edit: Norton/Symantec changed Ghost somewhere around 2002-2005ish to be more of a Windows backup program rather than a small bootable imaging program so when I said "an old copy" I mean it. You can sometimes find it on Ebay or, well, I'm sure you know of alternate methods.
You could also just zip everything up if you like - make sure to include hidden and system files - your archive software may exclude those (or at least hidden files) with default switches. If you go this route, you'll want to use a boot disk and use the command "sys" (and possibly need to also go into fdisk and set active partition) to get the system files copied properly. Honestly try to avoid this option if you can unless he insists on you sending him a standard zip file.
HDDs are usually not backed up into ISO... Usually it's either a proprietary format or a standard archiving type format like GNU tar.
Yes, I always ramble this much.