There are different reasons why a boot drive may becoming inaccessible. If the computer gives the inaccessible boot drive error after a Windows update, then there are several things that can be done.
The following are some methods to try to fix the inaccessible boot drive.
- Run a virus scan
- Check SATA hookup
There is a possibility that the computer had a virus and it was triggered by the update, these are called boot sector viruses. Use a antivirus program to preform a deep scan of the system. If it is unable to find the problem, then move on to the following option.
Try checking if the computer uses a serial ATA or SATA hookup, if so try switching from AHCI to ATA or vice versa. If the computer is using a BIOS 7 or greater, this can be done by pushing F10 when restarting the computer, so that the computer setup starts. Go to storage options under the storage tab, In storage options, select either AHCI or SATA.