If your P4 has the "Prescott" core then you can expect it to run hotter than expected. The temps that you quote are about right.
You need to get a little more concerned if it gets to around 72/73 degrees. I have an alarm set on mine at 74; it has never reached that and rarely gets to 70.
Higher fan speeds (with the original fan) can also increase the overall case temperature and in turn reduce the effective cooling of the processor, not to mention the irritating noise. I have experienced this problem and invested in a Zalman fan.........excellent, lower P4 temps and hardly any noise.
Regards
SHL