Window 10 Bootup time at least 20 minutes.

What Programs do you have opening on Start-up?

Also, what Security Software are you running?

Firefox, Ccleaner and Norton. The rest are system specific. Thank you for your time.

Use CCleaner to close all Start-up programs except Norton

How much space have you left in your hard drive. maybe run chkdsk.

Also run cmd as administrator and type in sfc /scannow and see if it finds and fixes any problems.

And of course try running in safe mode to see if it runs any quicker on there.

Clean reinstall, check device manager to see if any yellow exclamation marks on it. and of course check your upload/download speeds to make sure you are getting a proper signal from your ISP. Not sure if Malwarebytes clashes with Norton or now but I would give it a try to see if it finds any Problems.

Did it all the time when you running on Windows 10? Or it happened after update the Windows 10 new version. And I am agree with Govan1x. Check Windows 10 disk usage, cpu usage, task manager. And check if your computer is setup as fast startup. click here

The problem appeared recently.Maybe around December 2017? HDD is 50% free. Power Manager is from LENOVO. I do not have the options for a fast start up. I restored to defaults. See how it goes. IS THE PROBLEM with the MONITOR?

Monitors are usually Plug-n-Play (PNP) and only display output from the PC so have no effect on boot-up time. The problem has to be in the PC itself but you have asked twice "IS THE PROBLEM with the MONITOR?" so what is making you think the problem may be the monitor? I suggest you look at updating all your drivers. You can use IObit Driver Booster (see click here to do this.

10 Bootup time at least 20 minutes

Once it's finally booted up, is your Windows performance generally fast and perky or is it slow too? If it's the former then the Windows boot-performance logs can frequently identify what's causing the problem. Let me know if you're interested.

Sorry I did not realise that your PC is an all-in-one so my plug-n-play comment is not applicable but the rest of my comment about updating drivers still stands. Also as Govan1x says run chkdsk but include the fix switch as well i.e. chkdsk /f C: (note the spaces). Your PC is now 5 years old and it may be your HDD starting to fail and chkdsk /f C: will fix things only temporarily. Also install Speccy (see click here which shows you the status (health) of all your PC components. The HDD is shown under "Storage".

The PC is not an ALL in ONE. Monitor is 10 years old, the little blue light blinks for 35 minutes - now not 20 minutes. After the screen comes on, everything is good speed wise. Yes, PC is about 5 years old, but I do not use it for more than around 2 hours daily usually. Lenovo keep the drivers updated and I check this reguarly. I have disabled almost all the start up programes and left only a few which do not use too much resources. It is driving me Nuts!! Thanks for your time.