Heres the deal, at work (computer retail store), networking was ran all thru the building, and for the display computers we used to have the internet on one of them, but we lost the IPs. So now we have the IPs for the host, and the DNS Servers, now we just need to find out the IP of the proxy that it runs from.

What is a good/working proxy scanner, or whats the easiest way to find the proxy IP?

PS. we cant get admin access anymore, so thats out of the question.