Попробуй это:
Сначала продекларируй ф-ции:
function SetupDiGetClassDevsA(ClassGuid: PGUID; Enumerator: PChar; hwndParent: HWND; Flags: DWORD): HDEVINFO; stdcall; external setupapi;
function SetupDiEnumDeviceInfo(DeviceInfoSet: HDEVINFO; MemberIndex: DWORD; DeviceInfoData: PSP_DEVINFO_DATA): boolean; stdcall; external setupapi;
function SetupDiDestroyDeviceInfoList(DeviceInfoSet: HDEVINFO): boolean; stdcall; external setupapi;
function CM_Get_Parent(pdnDevInst: PDWORD; dnDevInst: DWORD; ulFlags: DWORD): DWORD; stdcall; external setupapi;
function CM_Get_Device_ID_Size(pulLen: PDWORD; dnDevInst: DWORD; ulFlags: DWORD): DWORD; stdcall; external setupapi;
function CM_Get_Device_IDA(dnDevInst: DWORD; Buffer: PChar; BufferLen: DWORD; ulFlags: DWORD): DWORD; stdcall; external setupapi;
function CM_Locate_DevNodeA(pdnDevInst: PDWORD; pDeviceID: PChar; ulFlags: DWORD): DWORD; stdcall; external setupapi;
function CM_Request_Device_EjectA(dnDevInst: DWORD; pVetoType: Pointer; pszVetoName: PChar; ulNameLength: DWORD;
ulFlags: DWORD): DWORD; stdcall; external setupapi;
Затем используй процедуру:
procedure EjectUSB(); // Отключение флешки
const
GUID_DEVCLASS_DISKDRIVE: TGUID = (D1: $4D36E967; D2: $E325; D3: $11CE; D4: ($BF, $C1, $08, $00, $2B, $E1, $03, $18));
var
hDevInfoSet: HDEVINFO;
DevInfo : SP_DEVINFO_DATA;
i : Integer;
Parent : DWORD;
VetoName : PChar;
begin
DevInfo.cbSize := sizeof(SP_DEVINFO_DATA);
hDevInfoSet := SetupDiGetClassDevsA(@GUID_DEVCLASS_DISKDRIVE, nil, 0, 2);
if hDevInfoSet = INVALID_HANDLE_VALUE then exit;
i := 0;
while (SetupDiEnumDeviceInfo(hDevInfoSet, i, @DevInfo)) do
begin
if (IsUSBDevice(DevInfo.DevInst)) and (CM_Get_Parent(@Parent, DevInfo.DevInst, 0) = 0) then
begin
VetoName := GetMemory(260);
if (CM_Request_Device_EjectA(Parent, nil, VetoName, 260, 0) <> 0) then
begin
if (CM_Locate_DevNodeA(@Parent, VetoName, 0) <> 0) then
begin
FreeMemory(VetoName);
continue;
end;
FreeMemory(VetoName);
if (CM_Request_Device_EjectA(Parent, nil, nil, 0, 0) <> 0) then continue;
end;
FreeMemory(VetoName);
break;
end;
inc(i);
end;
SetupDiDestroyDeviceInfoList(hDevInfoSet);
end;