That sounds very hot to me.
The Athlon XPs are considered hot running CPUs, and they usually run in the low 50s, sometimes up towards 60C under full load (with good, but air only, cooling my 2200+ runs between 47C and 51C depending upon load, which seems to basically mean how long it's been running 3D graphics - nothing else heats it up much).
Do you have at least 2 case fans - one blowing IN in the front and one blowing OUT in th back? Assuming it's some kind of a tower case, you want the front / intake fan to be positioned low and the back / exhaust fan positioned high (since heat rises). I'm also assuming that you have working HSFs (heat sink fan assemblies) on both CPUs? If they're passive cooling only (heat sinks, but no fans), that would make a huge difference.
And there's always the possibility that the PIIIs just run extremely hot... Another possibility is that you're getting a bogus reading. Does your BIOS support display of the CPU temp? Or any software that came with the motherboard?