Are you rooted 2.1 or stock?

can you help me? I have the evo and was had it rooted 2.2 but, no tether, so, i heard that you could only get free tether if you were back at 2.1, so i went back to 2.1, still no tether, so i am trying to get back to 2.2 but am getting an error when running RUU update, i get error 171 and it wont auto boot into bootloader. HELP