Hi,
I have a EliteBook 8540p laptop.
This one is always work well and the bios had never been updated before.
To get now features for my laptop, I updated the bios with the one given in "Drivers and software" from http://h20566.www2.hp.com.
So the official website and checking the exact model of my PC.
HP Notebook System BIOS Update (International) 
F.50
8 Jul 2014
I do "Initiate a bios update", the process finished with success (it done a backup of my previous BIOS during the update). It end with a countdown and after the PC restart.
But when it restart => black screen and all LED on.
When searching in this forum, i see lot of people who had the same problem with the same laptop...
One had found a fix for this issue :
I quote :
Resolved, after several days and countless number of methods and flashing simple solution is that i downloaded first published bios from 2010 for this model: Link Steps are simple 1. You need USB stick (FAT32, not bootable) 2. Download from HP your bios update (extract them with win rar or 7z) (then extract file from ROM package, rename Rom.bin and efibios.sig according to your number of bios - you can find them in ver.txt) 3. Put files like this on USB Hewlett-Packard\BIOS\Current\68CVD.BIN Hewlett-Packard\BIOS\Current\68CVD.SIG SMC.BIN 3 Start Laptop and press Windows key + B (about 3-5sec) When you see that something read data from USB release keys (it's all about feeling when you need let off this keys, so probably you need to try several times) 4 After 1-2 minute laptop will restart and you get error (press enter) 5. From this step further is all easy (your OS is booting )
i've tried but doesn't work, i see capital lock always get appear and disapear infinity, my USB stick is read by the laptop, but still black screen...
Moreover, i don't have "SMC.BIN" file and not sure for the good update to restore for my laptop.
Thanks for help me
Best regards.