It looks like somebody updated the site incorrectly. Thanks for letting us know.
I've got a zip of all the projects available at
http://www.marksmath.com/tecs/files/TECS_projects.zipI just tested it using Windows 7.
[It looks like the archives on the site are 7-Zip files. 7-Zip is an open source archiver that handles zip files as well as its own higher compression format. Google for it if you're interested.]
--Mark