HP locks up on startup, 3 user A/C, Classic Shell on 2 A/C

Question

My HP Spectre intermittently locks up on startup, The computer has 3 user accounts and Classic Shell interface on
2 of them.
User account A: Windows 8.1 interface
User account B: Classic Shell
User account C: Classic Shell
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 with mouse is frozen.
But I can [cntr][alt][del] to sign off user account A. I can then log in normally to any account using its
password. Then all appears to work OK.
It is said on the Clssic Shell forun that "This can't be related to Classic Shell. None of its code runs before
you log in."

Answer 1

Hi, thanks for the help, Jaco.
I have tried your suggestions previously but no avail.
I finally took it to an IT and it turned out to be a very simple problem:  the F9 key was stuck (even though it didn't look like it), so and since this key triggers diagnostics during start up, every time I turned on computer the diagnostics screen would come up.  When we unplugged the keyboard, everything was fine again.  Guess all I needed was a new keyboard!
Thanks anyway!  Much appreciated.