Difference between diifferent SATA Operation settings in BIOS

Also forgot to add in BIOS it says "Onboard or USB CD-ROM Drive (not present) and my computer doesnt detect CD ROM Drive in my computer. Also, CD ROM doesnt show in device manager. I also changed optical drive, same problem.

Any ideas?

Depending on the computer, it should be set up to RAID AUTO/AHCI as that is the newest and fasted interface. However if that is not working and you get a blue screen upon booting, it sounds like your OS was installed while it was set to something different. I'd try each one until you can boot fully. What computer do you have?

I have dell optiplex 755 running on windows 7 64bit