My HP Spectre intermittently locks up on startup, The computer has 3 user accounts and Classic Shell interface on 2 of them. Intermittently start-up goes directly into user account A, buy-passing the account selection screen and the password window. I can move mouse pointer but no click. Control is frozen.

User account A: Windows 8.1 interface

User account B: Classic Shell

User account C: Classic Shell

I am new to Windows 8.1 and to Classic Shell.