HP Probook 450 G3 startup issues since windows update 2 days ago

[D35hi]

Hi,

I had done the windows update 2 days ago and it installed 2-3 updates (I don't quite remember which ones) and after restarting it worked fine.

Since yesterday morning it didn't start up and had stopped on the black screen where it says at the bottom to Press ESC to enter the Startup menu. After pressing ESC, F2, F8, F12 and Del repeadedly it went in the menu (Don't know which one worked TBH) and I was able to do the short diagnostic tests (Memory, Hard drive) and the results came back fine.  After that I restarted the pc and after sometime it went into windows. Then I tried to update the drivers from HP website and after updating the Audio driver the laptop won't turn on at all and now it shuts down on every attempt of starting up after a few seconds.

I can see loads of queries with this same issues in HP website, unfortunately none of them have got the solution.

I have tried the hard reset numerous times with various combinations afterwards to turn on the laptop {hard reset, no battery, turn on AC adapter}, {Hard reset, With battery, WITHOUT AC power adapter}, {Hard reset, with battery, with AC power adapter] and the laptop did get in to windows on a few occasions randomly, sometimes on battery and sometimes on AC power. There was no pattern.  However, I wasn't able to restart the pc on a single occasion and each time while restarting it won't load windows nicely, it would rather hand around on the black screen and then shuts down. 

I have also updated the bios and the laptop got into windows nicely afterwards but i could not restart the pc successfully.

All in all its a very frustrating situation, the laptop is only a few months old and still covered by warranty. However, it belongs to my organization and I am the only IT person here so I am giving it a go before sending it off for them to sort out.

Can anyone help please?

Thank you

D35hi