My Asus X71Vn laptop was working fine with two hard disks until I tried to install an SSD and made some other changes. Now it works OK if there is only one disk drive in any of the two bays -no matter whether HD or SSD. There is a BIOS warning "Can't detect TPM device" which I am not sure if it was there earlier. In any case, this model doesn't have a TPM chip and I don't use encryption so it shouldn't be a problem.
The problems start when I install a second SATA drive (or a USB drive during the boot). The boot sequence goes fine, both drives are recognized, but then it stops after checking NVRAM and starts over. During the reboot, it does not recognize the second hard drive and it does not appear in Windows 7 Disk Management, nor in Linux "fdisk -l".
All the drives work fine by themselves and in both bays, so the problem is not in any of the drives. Something happens when there are two drives simultaneously. My BIOS version is the latest for that machine (207). I tried to install an older BIOS, I tried to change factory defaults in BIOS but nothing seems to help.