Freeze(?) & Checkpoint error [004F]

Recently my oldsish Dell Inspiron has started freezing. I have set Win10 to never sleep and also not turn off the display either. However, when I come back after an uncertain amount of time, usually > 1hr, the screen is dark and off (the monitor detects no input so shuts off). If I try to "wake up" the computer by moving my mouse or hitting any key on the keyboard, nothing happens.

The fan is still running so the computer has not shut itself down. The only way forward is to hold down the power key until the machine does a forced shutdown. When I then restart the computer, after waiting one or two minutes, 95% of the time the fans start but the monitor show "no input". If I wait a while, or sometimes if I keep turning off and then turning on. eventually the computer will restart. On a few occasions I get a message that something went wrong and that I should contact Dell support about the boot failing at checkpoint [004F]. As I am long out of warranty and cannot really afford the $120(?) support fee I am hoping that someone helpful and with good knowledge might be able to help. 

I look forward to hearing some advice from someone in this community, thanks in advance

Stefan