GA-Z97P-D3 tries to boot from wrong drive

[sputnick]

I have recently updated my PC using Gigabyte GA-Z97P-D3 motherboard and although it has been working sometimes it refuses to boot telling me to boot from correct drive. I have two sata drives, one ( C )is the system drive with windows 7 on and the other is a spare drive for photos ( D ) drive. It was set up to boot only from C drive but when it fails I find that the bios only has the D drive and the two DVD drives. Why would it change the drive sequence. I can only get it to boot by disconnecting the sata cable then it boots OK.
I am confused with the settings in the manual.
Can anyone talk me through the best settings.What isUEFI and GPT, What boot selection should I have.
What Sata mode selection should I use. I have Intel core I5 cpu and using Windows & 64 bit o/s

[dmdilks]

I find that the bios only has the D drive and the two DVD drives.

I can only get it to boot by disconnecting the sata cable then it boots OK.

There is no settings that you can make. You have a hardware problem. It something to do with the connection. If this is SSD try use a sata cable without the locking clip.