Kalde Function fra klasse, fejl opstår

Hvorfor kan jeg ikke gøre sådan her?.. nu har jeg roddet med det en halv dag tror jeg!

Fejl:
Error    3    error LNK2019: unresolved external symbol "public: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl Functions::Test::ComputerName(void)" (?ComputerName@Test@Functions@@SA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) referenced in function _main    TCPServer.obj   




[Funtions.h]
#ifndef Functions_H
#define Functions_H
#include "Functions.h"

using namespace std;

namespace Functions
{
    class Test
    {
        public:
        static std::string ComputerName();
       
    };
   
}
#endif

[Funtions.cpp]

#include "stdafx.h"
#include "Functions.h"

using namespace std;

std::string ComputerName()
{
    WSAData wsaData;
    WSAStartup(MAKEWORD(1, 1), &wsaData);
    char ac[80];
    if (gethostname(ac, sizeof(ac)) == SOCKET_ERROR)
    {
        WSACleanup();
        return "Error";
    }

    WSACleanup();
    return ac;
}



[TCPServer.cpp]

#include "TCPServer.h"
#include "Functions.h"

using namespace std;
using namespace Functions;

int _tmain(int argc, char* argv[], TCHAR* envp[])
{
    std::string Name;

    Name = Functions::Test::ComputerName();

    while(_getch()!=27); //27 is ESC char
    return 0;
}