Compaq Presario CQ40 series AMD and Intel Compaq Presario CQ40 initially released in the time of Windows Vista, at that time many users downgrade to Windows XP and it was not an easy process. You will need SATA driver and a Slipstreamed DVD to install windows XP. After that Windows 7 announced and HP released drivers for Windows 7 for certain CQ40 series and variant. You will find certain model