Converting Mac pictures to a PC

I'm a former PC user and still pretty new to my Mac. Could you please tell me how I can take the pictures that I've burned to disc on my Mac and make them viewable to someone with a PC? I sent the disc to a friend but he said that he wasn't able to bring them up. If I were to load the disc back into my Mac, would there a way to make him a viewable version?

Thanks.

I use Toast to create a hybrid CD, which can be read on an Apple or a PC.