Strange time consumption in for loop

Hello Experts,
I have encountered a strange situation.
I have added the corresponding code and the TRACE results.
So basically, I have two / three (three in the example but it is the same behavior with only two for loops), and it is making a huge time consumption on certain index.
Usually, it takes 0 milliseconds, but sometimes, it will take 16 ms.
I am working with VC2010 SP1 with Windows 7 and under Debug mode.
Thanks in advance !

int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
	int nRetCode = 0;

	HMODULE hModule = ::GetModuleHandle(NULL);

	if (hModule != NULL)
	{
		// initialize MFC and print and error on failure
		if (!AfxWinInit(hModule, NULL, ::GetCommandLine(), 0))
		{
			// TODO: change error code to suit your needs
			_tprintf(_T("Fatal Error: MFC initialization failed\n"));
			nRetCode = 1;
		}
		else
		{
			for (unsigned int i = 0 ; i < 100 ; i++)
			{
				DWORD dwT1 = GetTickCount();

				for (unsigned int j = 0 ; j < 500 ; j++)
				{
					for (unsigned int k = 0 ; k < 500 ; k++)
					{
						int Position = 0;
						Position++;
					}
				}

				DWORD dwT2 = GetTickCount();
				TRACE(_T("Delai (%d) = %d\r\n"), i, dwT2 - dwT1);
			}
		}
	}
	else
	{
		// TODO: change error code to suit your needs
		_tprintf(_T("Fatal Error: GetModuleHandle failed\n"));
		nRetCode = 1;
	}

	return nRetCode;
}

Select allOpen in new window

Delai (0) = 0
...
Delai (5) = 0
Delai (6) = 15
Delai (7) = 0
...
Delai (14) = 0
Delai (15) = 16
Delai (16) = 0
...
Delai (28) = 0
Delai (29) = 15
Delai (30) = 0
...
Delai (63) = 0
Delai (64) = 16
Delai (65) = 0
...
Delai (98) = 0
Delai (99) = 16