Toast files are image files created with Roxio's Toast Titanium for the Macintosh operating system. Converting the image file to the more universal ISO image file format may be necessary if the computer does not have Toast Titanium installed or if the file is going to be used with a Windows based system. Mac OS X has built-in support for .toast files, allowing the user to mount them in the Finder and subsequently convert them to ISOs.
Double-click the toast image file (.toast) to mount it in Finder.
Open Disk Utility. Select Go > Utilities from the Finder's menu bar.
Highlight the mounted drive directly below and indented under the .toast file within Disk Utility's sidebar.
Select "New Image" from the navigation toolbar. Type a name and select a save destination for the new file. Select "DVD/CD Master" from the Format drop-down menu. Select "OK" to begin the conversion process.
Open the folder containing the newly converted image file. You will notice it has a .CDR extension. Double-click the text of the file to edit the name. Delete the ".cdr" extension, replace it with ".iso" A warning will pop-up asking if you want to change the file association from .cdr to .iso, select "Use .iso" Your toast file is now an ISO.