Here are the specs for your HP Pavilion p6823w Desktop Computer and its N-Alvorix-RS880-uATX (Alvorix) motherboard. The N-Alvorix-RS880-uATX (Alvorix) motherboard is HP p/n 620887-001. The motherboard is a microATX (uATX) form factor <24.4cm (9.6 inches) x 24.4cm (9.6 inches> motherboard.
I hope the CPU isn't an Intel i7 quad processor, as the specs point to the HP p6823w (QN642AA) being an AM3 motherboard with a dual core AMD Phenom II X2 521 CPU.
Most of these AM3+ Micro-ATX Motherboards should work with the AMD Phenom II X2 521 CPU. Please note that unless you use the same indentical HP OEM motherboard as a replacement, you will have to purchase a new copy of Windows and your HP Recovery Discs will no longer work. You may also have other minor issues with the use of a non-factory motherboard.
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