TeXworks expl3.sty error

Question

I am trying to check if minted is already installed in my computer. I successfully installed Python, distributed.py and pip as instructed in this tutorial. I am now trying to test the new package with the sample:

\documentclass[a4paper]{article}
\usepackage{fontspec}
\usepackage{minted}

\setsansfont{Calibri}
\setmonofont{Consolas}

\begin{document}
\renewcommand{\theFancyVerbLine}{
  \sffamily\textcolor[rgb]{0.5,0.5,0.5}{\scriptsize\arabic{FancyVerbLine}}}

\begin{minted}[mathescape,
           linenos,
           numbersep=5pt,
           gobble=2,
           frame=lines,
           framesep=2mm]{csharp}
  string title = "This is a Unicode π in the sky"
  /*
  Defined as $\pi=\lim_{n\to\infty}\frac{P_n}{d}$ where $P$ is the perimeter
  of an $n$-sided regular polygon circumscribing a
  circle of diameter $d$.
  */
  const double pi = 3.1415926535
\end{minted}
\end{document}

I tried generating the sample in my TeXworks but the log file says that expl3.sty not found even though when I checked the Package Manager, it is present.

Here is the complete log file for more information:

    This is pdfTeX, Version 3.1415926-1.40.11 (MiKTeX 2.9)
    entering extended mode
    (C:/Users/Username/Documents/LaTeX/minted.tex
    LaTeX2e <2009/09/24>
    Babel <v3.8l> and hyphenation patterns for english, afrikaans, ancientgreek, ar
    abic, armenian, assamese, basque, bengali, bokmal, bulgarian, catalan, coptic, 
    croatian, czech, danish, dutch, esperanto, estonian, farsi, finnish, french, ga
    lician, german, german-x-2009-06-19, greek, gujarati, hindi, hungarian, iceland
    ic, indonesian, interlingua, irish, italian, kannada, kurmanji, lao, latin, lat
    vian, lithuanian, malayalam, marathi, mongolian, mongolianlmc, monogreek, ngerm
    an, ngerman-x-2009-06-19, nynorsk, oriya, panjabi, pinyin, polish, portuguese, 
    romanian, russian, sanskrit, serbian, slovak, slovenian, spanish, swedish, swis
    sgerman, tamil, telugu, turkish, turkmen, ukenglish, ukrainian, uppersorbian, u
    senglishmax, welsh, loaded.
    ("C:\Program Files\MiKTeX 2.9\tex\latex\base\article.cls"
    Document Class: article 2007/10/19 v1.4h Standard LaTeX document class
    ("C:\Program Files\MiKTeX 2.9\tex\latex\base\size10.clo"))
    ("C:\Program Files\MiKTeX 2.9\tex\latex\fontspec\fontspec.sty"
    ======================================================================
    starting package maintenance...
    installation directory: C:\Users\Username\AppData\Roaming\MiKTeX\2.9
    package repository: http://ctan.cdpa.nsysu.edu.tw/systems/win32/miktex/tm/packages/
    lightweight database digest: 2b12adf201b76e6cb772a57dc48b7601
    pdflatex.EXE: Unknown archive file size.
    pdflatex.EXE: Data: expl3
    ======================================================================


    ! LaTeX Error: File `expl3.sty' not found.

    Type X to quit or <RETURN> to proceed,
    or enter new name. (Default extension: sty) 

Answer 1

(CW answer from comment; it's really a Windows problem, rather than TeX)

minted relies on an external program (pygmentize) based on Python. However the documentation says that Windows in not really supported by minted (section 2.4 of the manual); you may try installing Python and pygmentize as suggested there,