var
 mas:array of string;
 cnt:integer;
 f:texfile;
x:integer;
s:string;
begin
 assignfile(f,'name.txt');
reset(f);
cnt:=0;
 while not eof(f) do
   begin
     inc(cnt);
    setlength(mas,cnt)
    readln(f,mas[cnt-1]);
   end;
closefile(f);
.............
for x:=0 to cnt-1 do
 begin
  if copy(mas[x],1,pos(':',mas[x])-1)=edit1.text then 
   begin
    s:=mas[x];
   delete(s,1,pos(':',s));
    edit2.text:=s;
    break;
  end;
end;