HELP: nVidia nForce4 + Windows XP woes

Dell Inpsiron 531 uses nVidia nForce4 SLI X16 (430 MCP61) motherboard. However Dell stopped support & shipping home PC range with Windows XP - only Windows Vista (although they still support Windows XP for their business PC range). The nForce4 SLI X16 also has integrated nVidia GeForce 6150 LE graphics card plus RealTek ALC888 HD sound card. I downloaded the correct nVidia nForce4 motherboard, GeForce 6000 series graphics & RealTek sound drivers. I was able to do a clean install of my Windows XP and all the drivers I gathered. Everything looks working now. 1. But in my Device Manager I see one unknown device (Location: on Microsoft ACPI-Compliant System, Manufacter: Unknown, Device Instance Id: ACPI\AWY0001\2&DABA3FF&0). Does anyone know what this is? Something to do with SATA harddrive? 2. Also, currently I have AMD64 X2 CPU. Is it true that I can also put in LGA775 P4? 3. Since am using AMD, is there optimizers to make it run quieter, etc?