Wine now also has precompiled binaries available. Together with WineBottler (an application to prepare and pack Windows applications for redistribution with Wine), it is available here: http://winebottler.kronenberg.org/.
Wine is an application which allows to run Windows application on linux, BSD or Mac OSX. Rather than full emulation, it acts as a compatibility layer between the application and the OS.
Wine is not entirely foolproof just yet; there is still much to be done, but with each passing release, more and more applications are getting supported.
Create a folder with the contents you want on your ISO.
Open Disk Utility and use the New Image from Folder menu item to create an image. Ensure it is uncompressed and use the CD/DVD master option.
In my experience this creates HFS+ masters which are no good in Windows.
Open the Terminal
Assuming your new image is called ~/Desktop/Master.cdr (the file is on your desktop and called Master.cdr) type:
cd ~/Desktop hdiutil makehybrid -iso -joliet -o Master.iso Master.cdr
This will create an ISO/Joliet .iso file.
A friend of mine had this problem with her camera storage thingy. If you're a MacOSX user, you might want to read up on the symptoms and solution on her blog.
Extra thanks go to Heidi for this.
