compiling dia in windows "cl" not found

[Meik Wusterhausen gkss de]

Hi,
I have problems to compile dia in Windows with the Tutorial on 
[dia-installer.de] from Steffen Macke. Hopefully you can help me.
Until the topic -Additional sources for the MSVC build- everything works 
perfect and is matching exactly with the explanations and illustrations. 
But then unzipping the additional sources generates the folder -gtk- with 
subfolders -bin- and -glib-. Why should I now erase the -GTK- folder (from 
the tutorial steps before) by unzipping the new folder to c:\ according to 
the text? Finally I added the content to the folders. Is this correct?
After succesfully starting -diadev.bat- in the next -Compilation- topic, I 
was not able to use -nmake-. So I downloaded and added -nmake.exe- and 
-nmake.err- to folder -c:\gtk\dia\- and then it was possible to start 
nmake. Do I need to set some environment variables to use -nmake.exe- 
another way or from another location? 
After starting -nmake makefile.msc- I got the error message -Der Befehl 
"cl" ist entweder falsch geschrieben oder konnte nicht gefunden werden.- 
Which means: "cl" is maybe written wrong or was not found. At this point 
(and as a newbie) I don't know how to find a solution.

Thanks for your help!!!
Best regards
Meik Wusterhausen