On my PC, I am unable to open any Windows apps such as Calculator, Windows Store, Camera, etc. Can someone help me? I even tried to reset my PC, but it did not work.
Your Title doesn't appear to the same as the question/problem. Used to be the Z: drive letter was automatically assigned to a NAS/Network Attached Storage drive with a second drive getting Y: and more moving back up the alphabet. But that changed with the last couple three versions of Windows. I assigned Z: out of habit to my NAS drive and can reach it from any computer I Map it on.
For the Apps issue did you run SFC /SCANNOW from a Command Prompt to check for corrupt files? If there's corruption a reset may not have fixed it.
There is no information given about the computer and Windows Version and Build.