it's not the CD that's incompatible as such, it's the image files on it. Some image formats are not cross-platform, you have to save them according to whether they are for for PC or Mac (the 'byte order' is different but don't ask me to expand on that please!).
From memory, I think TIFF images have to be saved according to the intended platform (where the option is available). Where no option exists then it will only be compatible with the host platform, or the chosen format is cross-platform.
JPEG format images, however, are cross platform I think, without any platform option required, but I can't swear to that.
The last time I gave some images to a mac owner from my PC, they were in TIFF format (to preserve quality) and I used the "save for macintosh" option in Photoshop. He had no trouble viewing them on his mac.
Unfortunately, not all image editing software gives you the choice of which platform to save the image to even when using a format that's not cross-platform. You'll have to ask your friend which image-editor he uses and to check what saving options it has. If he sent you TIFFS, ask him to save as JPEGs instead and try those.
Edited by pip22, 28 November 2006 - 03:28 PM.