I think you are looking for

Icon generator software.

When I search for that with Google I do see some options, eg the first one on the list for me was;

I have no idea how well it works. CNET's Download.com also has one here, http://download.cnet.com/Icon-Generator/3000-2195_4-10578424.html but the first review wasn't very good.

However that page did lead me on to Microangelo's Icon maker, a recognised name from some years back. Their web site at http://www.microangelo.us/

As with all of these, see if you can try before you buy. That way you have some time at least to evaluate the software.

I hope that helps, and good luck.