You could try this for older versions of Training Center: http://www.gawisp.com/perry/forerunner/
Hello Bill, I'm writing from Italy as I have exactly your same problem. I have tcd files created with Training Center that are not anynore possible to be opened. Currently I have the version 3.6.5 installed on my computer, but it can open just tcx files (also created with Training Center). Could you be so kind and guide me on what I should make? Thank you
Andrea
I think you'll need an even older version of Training Center. I have Training Center Legacy Version 3.5.3, which I believe uses the tcd database. Once opened, you should be able to export as TCX files out of Training Center, then import into Garmin Connect. Very tedious process. I can test later when I get some time.
Thank you very much! I wait for news from you :-)
Might be able to get an older version of GTC from allory. If not, I have 3.5.3.
I tried to write him, waiting for his answer. Thank you, you're very kind. In case, I'll ask you 3.5.3