So at work(im a developer) we have some old software package upgraded from vb6 to .net 1.1 at some point.  There are no copyrights on the software from my searches.

My company wanted to buy the source at one point recently, and original developer has more or less ignored us, but we believe he is out of business(10 year old software roughly), and we cannot find a current business by same name as him.

I need to keep software pretty much the exact same as it is now, due to laborers using it, and they dont take well to change!  So my version will look and feel identical, however code will not match up to original if we get sued.

What are the legal rights at this point? its more or less abondonware, and no copyright, different code than original by end of development.  The original developer has no legal right essentially at this point?

No doubt, it kinda of sucks, our company wrote the spec and had someone write it, however never thought to include having the source code for it. 

Thanks for the reply Nye, makes me feel better about it.  I may have to have my director talk to a lawyer about this anyways just to cover my ass.

If I understood what you said right, which is your company hired the original guy to program to their specs, your company is effectively the owner if software anyway, including any source code (which is missing naturally). You can do whatever you want unless the company wants to sue itself...