[SOLVED] pc not working,blue screen says kernel security check failure

Jan 2, 2020
My friend has just sent me some screen shots of his pc,he has a problem he switched it on yesterday and it keeps restarting and going through the same screens so he hasn't be able to use it
The first blue screen says your pc ran into a problem and needs to retart we'll do it for you,the stop code on the blue screen says Kernel security check failure,it then goes through the 3 screens continually.Those screens being the blue screen with the message then the Dell start up page,then a screen saying preparing automatic repair,but nothing happens apart from those 3 screens appearing again

He can't use it to get on the internet to see how to sort this out as it wont go past those screens,so phoned me and I thought I would ask on here

It is an old dell optiplex that is now running windows 10,I would have added the screen shots but don't know how too