This is what they told me---
Users who purchase the CD didn't used to be able to use the download feature. It has been added as a complimentary convenience for ONE platform only--to download to a Mac OR a PC--NOT BOTH. If you use the download feature for your Mac, you will not be able to use it for your PC and vice versa. In this case, you would need to use the CD to install on your other device. Apparently you can use the CD to install TT for multiple computers (5 total times) if you intend to use on both a Mac and a Windows PC. An external CD reader is necessary for many people who have devices which no longer have a CD drive built in.
