I will advise you to hold back on the overclocking, unless this is some secondary rig.
In this situation, it looks like you have a decent mobo, with the nForce2, which should help with it's AGP/PCI locks. Before overclocking, make sure you LOCK them down.
Also, it looks like your RAM isn't going to help this situation, with the PC2100 rated speed. You'll have to switch up the CPU:DRAM ratios to about 5:4, so your RAM wont be hold you back as much.
40-50 degrees celcius is awesome. looks like 2ghz is possible!
i dont know about how much the XP's can take, but if you have some temperature alarm feature, set it to somewhere around 70C. It should provide you with a good early warning.
Feel free to ask any questions.
One thing i have to ask: Is this a Palomino or a Thoroughbred?