My Radeon 4870 temperature.

I'm just wondering, I have my Radeon for 6 months already, and I've been checking around the temperature and I seem to receive a different result than what other people get.
My Radeon on idle with 50% fan speed runs on around 47-45c , and when I'm playing a game it can reach all the way up to 67c with 50% fan speed.
Just wondering whether these temperatures are normal or should I be worrying?

And another question, if I set the fanspeed to 100% could that damage anything?

Thanks in advance.