PowerISO is a utility which in short is to either create data disks or extract data from disks.. I've never actually used it so I'll outline two possible ways of using it..
1. If you place the disk in your drive, then start PowerISO and click extract. It will then ask where and what needs extracting, this is where you point it to your D drive (or whichever letter denotes your disk drive). I'm sure if you clicked on Help which is usually located at the top right hand side of the PowerISO box it'll give you guidelines on how to proceed.
The website has a FAQ and on extraction it says:
Q: How to open ISO file and extract files from it?
A: Because of its file associations, you can open an ISO file by simply double click on it. After open...