Soy un usuario de Linux Mint 15.
Quería escribir un programa simple en C.
Abajo está mi código. (Hw.c)

#include<stdio.h>
#include<conio.h>
int main()
{
    printf("Hello World");
}

Pero, cuando intento compilarlo con gcc

gcc -o hw hw.c

me da un error

hw.c:1:18: fatal error: stdio.h: No such file or directory
compilation terminated.

Busqué en Google y encontré algunas soluciones que dicen instalarbuild-essential
y trató de instalarlo

sudo apt-get install build-essintial

Pero vuelve a dar un error. El error es

    Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 build-essential : Depends: libc6-dev but it is not going to be installed or
                            libc-dev
                   Depends: g++ (>= 4:4.4.3) but it is not going to be installed
                   Depends: dpkg-dev (>= 1.13.5) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Entonces, ¿qué está mal? ¿Cuál es el problema?
¿Cómo resolverlo?

PD. El resultado delocate stdio.h es

/usr/lib/perl/5.14.2/CORE/nostdio.h
/usr/lib/syslinux/com32/include/stdio.h