Deleting the number of lines without using other files

/*
 * DeleteTrace.c
 *
 *  Created on: Feb 1, 2011
 *      Author: Karthikeyan.D
 */
# include <stdio.h>
# include <conio.h>
# include <windows.h>
# include <stdlib.h>

int main()
{
    // Variable Declaration
    FILE *FRead,*FWrite;
    char SzContent[1000];
    long int nloop;
    long int nLineIndex;
    /* File read and Read/write Mode Operation*/
    // Here You Can Your File Location.

    printf("Enter file File Path \n");
    gets(SzContent);

    FRead = fopen(SzContent,"r");

    FWrite = fopen(SzContent,"r+");
    if(FRead == NULL)
    {
        MessageBox(NULL,"Please Specify Already Created File Location ","Error in File Location",16);
        exit(0);
    }

    printf("Enter the Line Index \n");
    scanf("%ld",&nLineIndex);

    /* This function is used to remove the number lines*/
    for (nloop=0;nloop<nLineIndex;nloop++)
    {
        fgets(SzContent,1000,FRead);
    }
    /* This function is used to overwrite content from the top of the line*/
    while(fgets(SzContent,1000,FRead)!=NULL)
    {
        fprintf(FWrite,SzContent);
    }
    /* To close the Two File Pointer */
    fclose(FRead);
    fclose(FWrite);

    getch();
    return 0;
}