Must be my night for replies here.............If the file you downloaded is an Iso file you shouldnt use winrar..........Try a program such as UltraIso.
Iso files are basically an image file of a cd or dvd. UltraIso will when used allow you to burn the image back to cd or dvd as a replica of the original disk
There are other programs that will do the same job, eg, Alcohol120 etc , but I use UltraIso as it is pretty simple