In spite of the assertion, it is not pirated. The ISO image was downloaded as part of the Microsoft Developers Network Academic Alliance. I was just guessing the license was in the file since that was the arrangement with the other software I got the same way and installed without difficulty. The license allows installation on as many computers as I wish, provided they are for my personal use, not commercial or any other use, and my use only. But, I can only download the file once per semester and it is a long time until the next semester. Authorization and authentication is through the university's registrar and identification is through my student ID. I know I do not know all of Microsoft's business practices, and I suspect you do not know them all either. Anyway, I have two retail WinXP CDs. They each belong on a single system. I wanted to add WinXP to a system I use for experiments and testing. I will round up and try the various suggested programs, and other archive manipulation programs. I'm not expecting any progress, since it appears the error is detected in MS code that is probably called by all such programs. The original request was for programs that would check a file to determine if it was a valid .iso file and report the errors. I have not even been able to find a spec of the file format. I found the ECMA version of ISO 9660 covering the format of the CD, but absolutely nothing about the internal structure of a .iso file. No BNF, no TLV, no SDL, no Pascal Railroad Tracks, nothing at all.