I took a CD-RW disc and used InstantBurn 3 to format it. It formatted the CD and said I could write to it like a floppy, but I was unable to read that disc from another CD-ROM drive.

InstantBurn 3 uses UDF format writing and only a computer with UDF software will be able to read the content of your CD-RW. You can download a UDF Reader from our website, as well. Also make sure that the PCs under which you are trying to read your files have CD-ROM drives with multi-read capability.