Installing second processor

Hello,

I would like to know if anybody around heres knows anything about installing a second processor, and what steps it would involved?

I currently have configurations set up for my computers BIOS:

Brand/Model: HP Pavilion 05 P9859A-ABA 533w
BIOS: Phoenix Technologies LTD 6.00 04/25/2003
System Board: TriGem Computer Inc. Glendale Motherboard
Brand/Model: Intel Celeron
Nominal Clock Speed: 2000 MHz
Measured Clock Speed: 2000 MHz

And the current processor I am wanting to add on to the motherboards BIOS is a 766/128/66/1.7v Intel Celeron 766 MHz processor, 1.7 volts; and I have a large enough power supply to run all this.

I am looking for answer to these questions:

If I do decide to install a second processor, what would I have to buy for my system; if any.
And will it work with my current operating system (Windows XP) without having to reinstall it; and/or BIOS.

Thank you if any body have a answer to these questions, I would really like to hear them.

Thank you.