The basic installation of MiKTeX doesn't download the Type1 fonts for the Computer Modern fonts in T1 encoding (actually the European Modern fonts are used, but they are very similar to Knuth's CM). Since the compiler doesn't find Type1 fonts, it includes the bitmap version obtained by running Metafont and converts it into a Type3 font.
The required Type1 fonts are provided by the CM-Super package, that you can install with MiKTeX's package manager.
Alternatively you can specify to use the Latin Modern fonts (again very similar to CM), that should be available in the basic installation:
\usepackage{lmodern}
Since this changes also the text fonts, and from your comment I gather that the minionpro package doesn't change the monospaced font family, you can do
\usepackage{lmodern}
\usepackage{minionpro}
so that the second call overwrites the text fonts chosen by the first one.
Another way would be to change only the monospaced font family:
\usepackage{minionpro}
\renewcommand{\ttdefault}{lmtt}
as lmtt is the name by which Latin Modern Typewriter is known to LaTeX.
Best Answer
As far as I can see from the screenshot, the fonts used are the standard LaTeX fonts, i.e., Computer Modern (Roman, Boldface, and Italic; together with the standard LaTeX math fonts). They look like 300dpi pixel fonts (300dpi was a de facto standard resolution of laser printers for a long time in the past).