Hey there again, @Shelley_9!
Do you hear the hardware power up whenever you get the Black Screen of Death and switch on the laptop? If it does work, the issue could be in the display itself, so you could also try connecting an external monitor to determine if the issue is coming from the LCD on the laptop. If the problem is still present afterwards and resetting BIOS doesn't change anything as well, I'd totally agree with @tekno2go and second the suggestion to change the CMOS battery.
If you don't want to do this by yourself, I'd definitely advise you to end the struggle of DIY troubleshooting and get the laptop to the nearest PC repair service shop and let the guys there perform full system diagnostics. They could easily help you...