compiler error question

Hi All,
  I need a function that adds an extra backslash to a file path that is
returned by another function. I couldn't find any examples anywhere so I
wrote one of my own and when I compile the code I get the following error:

error C2666: '[]' : 2 overloads have similar conversions

what does that mean? I wrote the original code on another dev machine and it
works perfectly but when I copy the code to another machine, the one I'm
sending this email from in fact, I get that error. the code I am using is
written below.

int main(int argc, char *argv[])
{
    char str[] = "C:\\This\\is\\a\\test.exe";     //test path functional
verification

    //cycle through the string and add an extra backslash character
whereever a single backslash is found
    for(unsigned int X = 0; X < strlen(str); X++)
    {
         if(str[X] == ' \\ ' )         //error is here
         {
               printf("\\");
         }
         printf("%c", str[X]);      //and here
    }
    printf("\n");


   //other code

return(0);
}