I have an ASUS Q504U with an i7, 16 gigs of RAM, 128 m2 SSD and a 1 terabyte HDD with Windows 10 operating system. The laptop is approximately 18 months old and first started to fail a week ago. It does not recognize the one terabyte HDD. So thinking that the HDD was bad I removed it and installed a 500 gig crucial SDD in its place. After properly installing the sdd the laptop still does not recognize the harddrive. It sees the hundred and twenty eight gig factory-installed SDD but does not see the 500 gig crucial SSD I installed.