I've done several installations, using different techniques. So I have experience, not a noob. On two particular machines, a Latitude D630 and an Optiplex 745, the OS X installer does not recognize any SATA drives are connected. Installation is from a USB stick. BIOS settings are all correct, SATA channels are enabled, AHCI, etc. These machines boot fine from Windows 7 installed SATA drives. I have tried both drives with Win 7 already installed (GPT and MBR boot), and completely blank drives, GPT pre formatted to HFS+. None are recognized by the OS X installer. Once in the installer, I run Disk Utility and it doesn't see any SATA devices, including the SATA DVD/CD drive. Running System Profiler under the Utitlities menu of the OS X installer also shows no SATA devices detected, including the DVD drive. Disk Utility shows the only disk device connected is the USB stick that I'm booting from. I've tried disconnecting the DVD drive and have only the hard drive as the only SATA device connected, and that doesn't change anything. I am booting from the USB stick using the F12 Boot Option Menu that is typical on Dell machines. In the Dell F12 Boot option menu, it DOES show the SATA drive as an option to boot from, so at that point, the system and BIOS is recognizing SATA drives just fine. Any ideas?