Whts ur ambient temp & case temp ?
Generally, 54C is slightly high but if ur system is stable...dun bother.
I tested on Asus A7V133 w/ XP 1500+. Temp as follow: -
Ambient = 30C
Case temp = idle@38, f/load 39C
CPU temp = idle@51C, f/load 55C
Running on stock cooler w/ pad. Stable as rock.