Slot 1 Upgrade

[a1rocketpilot]

I am planning to upgrade my brother's old pc (Dell XPS B800r) by putting in a new processor. I've found various solution from Slotkets to the PowerLeap PL-iP3/T. Does anyone know the processor limitations of the motherboard used in this pc (I don't have the chipset offhand, I shall try and get the make soon)? Also, what is the difference, both real and practical between the P3 and the P3 Celeron and the Tualatin and Coppermine cores?