Windfall, we are trying to help you, but you are being very evasive by not answering very simple and basic questions like a directory of the files you are trying to operate on or even the complete names of the files.
You said they were iso files with RAR inside of them, "I have a program I bought--which consists of iso image files( dvd)--in 2 parts
both have another winrar file pack inside each other". How hard is it to even list those names, like
You wouldn't even tell us what you were using to unpack or how?
'Compressed' files usually will come in a few extensions, RAR, 7Z, and ZIP generally. Images will come in a few too, like ISO, BIN and CUE pair, and others. Then there are the Split/Join set that have number extensions, like 001, 002, ect.
All these need different unpacking methods.
You indicated you got RAR files after unpacking the ISO's. Fine, but you refuse to name the files? Why?
Many 'pirate sites' and newsgroups use RAR as a compression method as do MANY legitimate s/w producers and vendors. However, your unwillingness to detail what you got and where from leads me, and I assume others, to suspect your reluctance to give full information means to us your source is not legitimate? I googled as you said and not only was I able to find the supplier, but cracked and torrent copies as well. This is an $1,800 program, but you can get it 'free' HERE</ a> as well.
I checked their Nuendo's FORUMS to see if others had installation problems or asked how to install it? None that had to do with the method, mostly about dongle problems (if you've got a crack, this wouldn't be needed) or license problems, but none on how do I install or decompress the disk images?
They tell you to look at the PDF on the program CD/DVD's if you have a problem. Registered users (if you have a legitmate copy) can even call them?
Sorry, with your attitude and evasive non-answers, one can only draw the conclusion that you do not have a legitimate copy, and I for one, and I'm sure others here, well not help you unpack a pirated copy, even if you bought it from a pirate.