iirc u are fine up to 80.C with that cpu.
it could just be warmer if its slightly more clogged up with dust etc....
u have nothing to worry about regarding the cpu.
have u run a game or anything to see what the temp rises to?

is the fan on the cooler running?
If they are old sometimes the thermal compound can dry and crack meaning the heat sink does not interface with the CPU properly, although those old P4s run very hot anyway. Also, it is categorically NOT faster than you dual core as the clock speed is not the only measure of chip performance. As an example, my laptop contains a 1.3GHz Penryn core 2 duo and has equivalent or greater single core performance to a 3.2GHz Pentium 4.
Running XP pro should not affect the temperatures at all, I've run home, windows 2000 and even windows Vista on a P4 system and the OS used did not affect the temperatures in any way. Differences are to be expected due to different heat sinks, thermal compounds, age, quality of CPU, case and even power supply dumping heat into the case.
