If it is a propretiary format like a Photoshop format or even jpeg it might not be readable some decades later. If you want to be on the save side, either copy a program which can read the files on the CD or use the tiff format, which is a far as possible approved to be supported by most of the readers in the future.
I'd guess that more future computers will be able to read a widely published document format, than run a program that's specific to the processor and OS you have today.
I.e. both TIFF and JPEG is more safe than any viewer program. Hey, quite a number of computers can't run your viewer program even today (Mac, Linux etc). But they sure can display a TIFF or a JPEG.
I work for a software comany which sells archiving software and we recommend tiff or pdf as a longtime format.
PDF is proprietary, too, just like PSD. I'd go with TIFF.
anders ------------------------- http://anders.hultman.nu/
