HANDLE snap = CreateToolhelp32Snapshot (TH32CS_SNAPPROCESS, 0);
PROCESSENTRY32 prEntry = {};
prEntry.dwSize = sizeof (PROCESSENTRY32);
if (Process32First (snap, &prEntry))
{
   do
   {
       if (prEntry.th32ProcessID)
       {
          HANLDE h = OpenProcess (PROCESS_QUERY_INFORMATION, FALSE, prEntry.th32ProcessID);
          // <<<< h is (-1) here
          if (h)
          {
              // do something
              CloseHandle(h);
          }
       }
   }
   while (Process32Next (snap, &prEntry));
}