Dev - C++ - Codigo del post anterior

Wenas tengo un codigo para un programa que monitorice el espacio libre de un disco duro pero tiene algunos errores asi que si alguien los pudiese revisar y mandarmelo arreglado se lo agradeceria.

Tiene comentarios en los lugares que falla.

#include <windows.h>
#include <winbase.h>
#include <iostream.h>
#include <iomanip.h>
#include <string.h>
#include <stdio.h>

void fmtnumber(__int64 Number, char FmtNumber[]);
void fmtsize(__int64 Number, double &Size, char Units[3]);

void main()
{
BOOL success;
LPCTSTR DiskDirectory = "C:\\"; // directory name
__int64 AvailableBytes; // number of bytes on disk available to the caller
__int64 TotalBytes; // number of bytes on disk
__int64 FreeBytes; // free bytes on disk
DWORD SectorsPerCluster=0; // pointer to sectors per cluster
DWORD BytesPerSector=0; // pointer to bytes per sector
DWORD FreeClusters=0; // pointer to number of free clusters
DWORD TotalClusters=0; // pointer to total number of clusters

char FmtNumber[20];
double Size;
char Units[3];

success = GetDiskFreeSpaceEx(DiskDirectory, (PULARGE_INTEGER) &AvailableBytes,
(PULARGE_INTEGER) &TotalBytes, (PULARGE_INTEGER) &FreeBytes);
if (!success)
{
success = GetDiskFreeSpace(DiskDirectory, &SectorsPerCluster,
&BytesPerSector, &FreeClusters, &TotalClusters);
FreeBytes = FreeClusters * SectorsPerCluster * BytesPerSector;
TotalBytes = TotalClusters * SectorsPerCluster * BytesPerSector;
}

if (success)
{
cout.flags(ios::fixed);
cout << setprecision(2);
fmtnumber(TotalBytes - FreeBytes, FmtNumber);
fmtsize(TotalBytes - FreeBytes, Size, Units);
cout << "Used space: " << setw(15) << FmtNumber << " bytes";
cout << setw(8) << Size << setw(3) << Units << endl;

cout << setprecision(1);
fmtnumber(FreeBytes, FmtNumber);
fmtsize(FreeBytes, Size, Units);
cout << "Free space: " << setw(15) << FmtNumber << " bytes";
cout << setw(8) << Size << setw(3) << Units << endl;

fmtnumber(TotalBytes, FmtNumber);
fmtsize(TotalBytes, Size, Units);
cout << "Capacity: " << setw(15) << FmtNumber << " bytes";
cout << setw(8) << Size << setw(3) << Units << endl;
}
cout << Size << endl;
}

void fmtnumber(__int64 Number, char FmtNumber[])//1ra funcion
{
const int LBUF = 14;
const int LFMT = 17;

char buffer[LBUF], fmtbuffer[LFMT];
char _i64toa_s(Number, buffer, 10);//lo midifique agregando el char pero falta (Convierte un entero a una cadena)
int l = strlen(buffer) - 1;
int n=0;
int icount=0;
int i;
for(i=l;i>=0;i--)
{
if (icount==3)
{
fmtbuffer[n]=',';
icount=0;
n++;

}
fmtbuffer[n]=buffer[i];
icount++;
n++;
}
fmtbuffer[n]=0;
//strcpy(FmtNumber, strrev(fmtbuffer));//a modificar porke falta algo
}

void fmtsize( __int64 Number, double &Size, char Units[3])//2da funcion
{
const int KB = 1024;
const int MB = KB*KB;
const int GB = KB*MB;
double DIV;
if (Number>GB)
{
DIV = double(GB);
strcpy(Units,"GB");
}
else if (Number>MB)
{
DIV = double(MB);
strcpy(Units,"MB");
}
else
{
DIV = double(KB);
strcpy(Units,"KB");
}
Size = Number / DIV;
}

Gracias de antemano.