wchar_t NameBuffer[MAX_PATH];
wchar_t SysNameBuffer[MAX_PATH];
DWORD SerialNumber;
DWORD Length;
DWORD File;
GetVolumeInformation(L"C:\\",NameBuffer, sizeof(NameBuffer),&SerialNumber,&Length,&File,SysNameBuffer,
sizeof(SysNameBuffer));
Источник: http://*****.com/board/showthread.php?t=495916&cdattempt=1