UINT64 -> double 형변환

error C2520: conversion from unsigned __int64 to double not implemented, use signed __ int64

//VC6에서는 UINT64 에서  double로 변경을 기본으로 지원하지 않는다.
//UINT64 -> double 변환 함수

double ToDouble(UINT64 _n64In )
{
    __int64 i64 = (_n64In & 0x7FFFFFFFFFFFFFF);
    double dbl = (double) i64;
    if (_n64In & 0x8000000000000000)
        dbl += (double) 0x8000000000000000;
    return dbl;   
}

//참고

https://groups.google.com/forum/#!topic/microsoft.public.vc.language/yZ8Jki4t9f4