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06G6JW Motherboard for Dell Alienware X51 R2 Mini-ITX LGA1155 Desktop – PC Part Source Inc.
Amazon.com: KM92T Fit for Alienware X51 R1 System Motherboard 1717 cm DDR3 H61 Lga 1155 Motherboard Original Desktop Mini Itx 0KM92T KM92gaming Motherboard Combo : Electronics