Viruses

I have a customer that recently had a really bad infection on their computer and a lot of finical infor was compromised.  They have since cleaned up the, but I am going to install a totally new hard drive in case there is something living on the boot sector or some kind of new root kit that has not been identified yet.

They have a lot of picture files.  Is there a chance that some of these picture jpeg files have viruses attached to them. I have never heard of it.  However, I seem to remember hearing something about that a long time ago, and can not remember the source.

Also, consider the source, but some tech said at a very large computer chain store said it was possible their router was infected, three gusess and the first two do not count. Never heard of that either.

Thanks very much for the help,

Rick