While JPEGS and TIFFS are cross platform file types it does not always work.
I use a ZIP drive and I am assuming that it would work the same for a PC. I
have to first initialize the disk on the PC. Take it to the MAC and put the
file on it and then bring it back to the PC. If you do not do the initial
step it will not work. This is not true of going the opposite way however.
You can scan on a PC and go right to the MAC with no problem with these file
types. An EPS file might also work. I recoommend using TIFF's wherever file
size is not a concern. JPEGS lose quality every time you open them and make a
change. TIFF's do not.
I work as a graphic artist and teach adult art ed on weekends so now you are
in my field!