The reasons UEFI/BIOS cannot access the drive can be caused by the drive, the data cable, the electrical system, the motherboard, or a loose connection. Here is a list of things to do and check before you open the case:

## Step1: Check UEFI/BIOS Error Messages
### If UEFI/BIOS displays numeric error codes or cryptic messages during POST, consult the manufacturer's website for explanations of these codes or messages.
## Step2: Verify Hard Drive Configuration
### Check UEFI/BIOS setup for errors in the hard drive configuration. If you suspect an error, set UEFI/BIOS to default settings, ensure autodetection is turned on, and reboot the system.
## Step3: Boot from Alternative Media
### Try booting from another bootable media such as the Windows setup DVD or a USB flash drive or CD with diagnostics software installed (e.g., Hiren's BootCD software). If you can boot using another media, the problem is likely isolated to the hard drive subsystem.
## Step4: Check RAID Array Status
### For a RAID array, use the firmware utility to check the status of each disk in the array and for errors. Press a key at startup to access the RAID UEFI/BIOS utility. This utility lists each disk in the array and its status.
## Step5: Interpret RAID Status Messages
### Search the website of the motherboard or RAID controller manufacturer for an interpretation of the messages on this screen and what to do about them.
## Step6: Rebuild RAID Volume
### If one of the disks in the array has gone bad, it might take some time for the array to rebuild using data on the other disks. After the array has rebuilt, your data should be available. However, if one of the hard drives in the array has gone bad, you need to replace the hard drive and then rebuild the RAID volume.
## Step7: Rebuild RAID Volume
### How to rebuild a RAID volume depends on the RAID hardware you are using. For some motherboards or RAID controller cards, you use the RAID firmware. For others, you use the RAID management software that came bundled with the motherboard or controller. You install this software in Windows and use the software to rebuild the RAID volume using the new hard drive.