Here's the class it 'cries' about:
 Directory of d:\progz\java\teambots\src\tbsim

[.]                      [..]                     Makefile
SimulationCanvas.java    TBSim.java               TBSimApplet.java
TBSimNoGraphics.java     index.html               test.html
SimulationCanvas.class   TBSim.class              TBSimApplet.class
TBSimNoGraphics.class

Now, according to the installation instructions' on 'http://www.cs.cmu.edu/~trb/TeamBots/#INSTALLING', we have also to add:
 Directory of d:\progz\java\teambots\lib
18/04/2000  07:00 pm           259.265 collections.jar

And finally I do:
set CLASSPATH=d:\progz\java\teambots;d:\progz\java\teambots\lib\collections.jar;.

And 'd:<cr> cd d:\progz\java\teambots\domains\soccerbots\teams <cr> demo.bat<cr>'
It does a:
D:\Progz\Java\TeamBots\Domains\SOCCER~1\teams>java TBSim.TBSim robocup.dsc 511 3
00
Exception in thread "main" java.lang.NoClassDefFoundError: TBSim/TBSim

And returns to the prompt... :/
I have re-downloaded file some times to assure there's no file corruption at all.