Title: Get a user name
Use GetUserName for solving of this problem. For example:
procedure TForm1.Button1Click(Sender: TObject);
var
StrUserName: PChar;
Size: DWord;
begin
Size:=250;
GetMem(StrUserName, Size);
GetUserName(StrUserName, Size);
Label1.Caption:=StrPas(StrUserName);
FreeMem(StrUserName);
end;