CompuServe Messages

Help please, I have been having a problem transferring file from the Mac to the Amiga. I have a couple of questions that are all related. First, I have a Mac at home with the standard 4 Meg ram. At my office we have the Amiga 4000 that has the Video Toaster installed. What I want to do is transfer graphics files from the Mac to the Amiga and back. I did fine a program for the Mac that will convert IFF to TIFF and vice versa. When I brought back home some IFFs that I created on the Toaster and converted them to TIFFs, all I got on the Mac screen was black. I think it's because the Amiga has 20 RAM and my Mac only has 4. I have tried to reduced the file size from the Amiga, but it made no difference. Is this possible? Second, at home I use Compuserve on my Mac that also has a super drive that can read and write to DOS disks. I have tried to download several programs from the Amiga forum onto a DOS disk and then I took them to work. I was able to put them on the hard disk, but I can't seem to run them. I am not that familiar with the Amiga operating system. So, I am not sure why I can't run them. I have tried just clicking them, but all I get is a return code 10. The file extensions are .LHA, .Z00 and .LZH. I believe that these are compressed file. I called compuserve support and they said to Download LX.LHA, which is supposed to be a self extracting decompressing program, but I was still unable to run it. As I said before, I am very unfamiliar with the Amiga. I hope someone can Help me. Thanks Mark B.