pdfTeX error (font expansion): auto expansion is only possible with scalable fonts even with \usepackage[T1]{fontenc}

I will answer this question of my own for documentation purpose: MikTeX by default doesn't come with any scalable fonts that pdfTeX is happy with - who knows exactly what makes pdfTeX happy except cm-super... When using MikTeX, if encounter auto expansion is only possible with scalable fonts error, install cm-super fonts family, execute initexmf --mkmaps command in console, and add \usepackage[T1]{fontenc} to TeX document.

Well, I'm not sure but I think package lmodern should be part of the basic installation of MiKTeX.

Please see the following image. I called the MiKTeX Package manager and filtered for lm (Latin Modern). Then you can see if Latin Modern is installed, if you see an date in column Installed on. BTW: Do not forget to call package lmodern to activate Latin Modern in your TeX document ...

On the other side you should be able to install it later with the MiKTeX package manager, like you tried with cm-super.

Now to the last sentences of your question:

In windows you can open the terminal/console with:

Windows-key+R, type cmd, press enter and type the mentioned command into the new window: initexmf --mkmaps, then press enter ...