You should copy the file to the Windows\Fonts directory, then add an entry to the registry key: "'Software\Microsoft\Windows\CurrentVersion\Fonts". The entry will be the font name and the path (if different than the Windows\Fonts directory). Once the registry entry is written, you should make a call to the Windows API function AddFontRecource(), then broadcast a system-wide WM_FONTCHANGE message. Finally, you should make a call to the Windows API function RemoveFontRecource(), to remove the resource lock on the font file, and broadcast a second system-wide WM_FONTCHANGE message. Here is an example: uses Registry;

procedure TForm .Button Click(Sender: TObject);
var
  reg: TRegistry;
  b : bool;
begin
  CopyFile('C:\DOWNLOAD\FP000 00.TTF',
           'C:\WINDOWS\FONTS\FP000 00.TTF', b);
  reg := TRegistry.Create;
  reg.RootKey := HKEY_LOCAL_MACHINE;
  reg.LazyWrite := false;
  reg.OpenKey('Software\Microsoft\Windows\CurrentVersion\Fonts',
              false);
  reg.WriteString('TESTMICR (TrueType)','FP000 00.TTF');
  reg.CloseKey;
  reg.free;
 {Add the font resource}
  AddFontResource('c:\windows\fonts\FP000 00.TTF');
  SendMessage(HWND_BROADCAST, WM_FONTCHANGE, 0, 0);
 {Remove the resource lock}
  RemoveFontResource('c:\windows\fonts\FP000 00.TTF');
  SendMessage(HWND_BROADCAST, WM_FONTCHANGE, 0, 0);
end;