Why can not I write to a physical drive in C language?

Why can not I write to a physical drive in C language?

I ran the code. At first I was successful. But it has been failing ever since.

Here is my code.

#include <Windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <tchar.h>

int main()
{
    char cur_drv[100];
    wchar_t text1[100];
    HANDLE g_hDevice;
    DWORD dwRead;
    DWORD dwpointer;

    char buf[512];

    int ret = 0;

    sprintf(cur_drv, "\\\\.\\PhysicalDrive%d", 3);
    mbstowcs(text1, cur_drv, strlen(cur_drv) + 1);
    LPCWSTR test = text1;

    for (int i=0; i<512; i++)
        buf[i] = '0';

    g_hDevice = CreateFile(test, GENNERIC_WRITE | GENERIC_READ, FILE_SHARE_WRITE | FILE_SHARE_READ, NULL, OPEN_EXISTINNG, FILE_ATTRIBUTE_NORMAL, NULL);

    dwpointer = SetFilePointer(g_hDevice, (0<<9), (0>>(32-9)), FILE_BEGIN);

    if (dwpointer != 0xFFFFFFFF)
        ret = WriteFile(g_hDevice, buf, 512, &dwRead, NULL);

    CloseHandle(g_hDevice);

    return 0;
}

After running the above code, check the hex value. I Checked hex value. At first I was successful. However, it is not written after that. When the ret value is printed, it is initially 1, but after that it is 0. What is the reason?