Converting WinRAR (.RAR) files to an .ISO (burnable CD/DVD image) format is not a simple, one-step process. It would seem like an obvious choice for a software package since disk images are often distributed in a .RAR package. But the technologies involved in compressing a .RAR archive and writing an .ISO image are quite different and solutions claiming direct conversion are often inconsistent in their results.
Obtain WinRAR software (see Resources) or download a free, multiplatform archive and compression utility like PeaZip. Either option will work well. PeaZip has the added benefit of built-in ISO support, meaning you'll only need one software package instead of a separate .ISO imaging solution in later steps.
Open up WinRAR (or whichever compression utility you've decided on). In a separate Windows Explorer window, locate the .RAR file (or files) you want to convert to an .ISO image. Drag the .RAR file into the compression utility's workspace. Choose the option "Extract All" and unpack the .RAR to a location on your computer.
Once the .RAR has extracted completely, exit WinRAR.
Obtain MagicISO or other .ISO imaging software. Again, several excellent free options are available. PeaZip can pack files to an .ISO image as well as working as a multiformat compression and extraction utility.
Open your .ISO imaging software. Again, open a separate Explorer window. This time, locate the unpacked contents of your .RAR file and drag them into your imaging software's workspace. Then choose the "Create Image" option (the wording may differ from program to program, but it should be fairly self-evident as creation of the image will be the main function of the software.) Some imaging programs may not allow drag-and-drop. In these cases you will have to choose "File, Open" or "File, Add" from the menu bar and then go to the files you extracted from the .RAR before creating the image.
Burn the .ISO to a CD or DVD. You can then delete the .RAR source, unpacked files and .ISO image file to save space on your hard drive.
Things You'll Need
WinRAR or other RAR-capable archive software
MagicISO or other ISO-capable imaging software
Sufficient hard disk space to store disk images
Do not download or create images of any illegally distributed software.