DAEMON Tools is pretty popular, but I'm sure there's other software out there that does the same thing if you don't like it.
Here's the download page: [LINK]
There's four items on that page. The first is DAEMON Tools Pro Advanced Evaluation, the second is DAEMON Tools Pro Standard Evaluation, the third is DAEMON Tools Lite, and the last one is DAEMON Tools toolbar. If you're not gonna buy it, just download the third one. It should be able to do everthing you need. The first two are just 20 day evaluation versions that come with all the bells and whistles. And that last thing is just a web search tool.
Once you get it installed, there will be an icon in your taskbar that looks like a purple bolt of lightning. To mount an ISO image, right click the icon and go to Virtual CD/DVD-ROM, highlight one of the virtual devices (you can set up to 4 of these), and click "Mount image." A browsing window will pop up, and then all you gotta do is find and select the ISO file. 