Paolo, any luck getting this computer to work correctly with Win10?
See if it is possible to replace the Video Card with something better/newer. Its a long shot since this is a Laptop... But you might get lucky. Some Laptops have removable card inside, and if this is the case, you can upgrade it. For Windows 10 the Video Card (or more specifically, its Driver) needs to use WDDM 2.0 or better. WDDM is basically the "blueprint" a company creates the Driver from. Without WDDM 2.0 it will, in short, fuck everything up royally. You'll get the exact effects you were describing: Resolution changes, can't run Direct3D (or can only run part of it), WindowsUpdate constantly looking for new Drivers, no Sleep mode, Start Menu seeming to dissappear (its below the bottom of the screen). When looking for a new Video Card, find one that specifically says it is compatible with Windows 10 -- that means it has a WDDM 2.0 type Driver (some Manufacturers won't mention WDDM 2.0 at all, or it will be buried in the fine print).
Also if you haven't already, look for Drivers at both the Video Card manufacturer (probably AMD/ATI or NVidia, maybe Intel) and the Laptop Manufacturer website (Lenovo). Sometimes the "Legacy" Drivers from the Video Card Manufacturer work better.
If it isn't possible to replace the Video Card in the Laptop, or get a WDDM 2.0 Driver for it, the only option for a usable computer is to go back to Windows 7 or switch to Linux. Or if your Boss is set on Windows 10, buy a new computer that comes with it pre-installed. The Windows 7 CD Key for the Laptop should still work even after the Windows 10 upgrade. I've re-installed Win7 on a few systems where Win10 didn't work right, no problems it activated just fine. You can download the Windows 7 ISO from Microsoft, or a Linux ISO from dozens of websites (links below). With the ISO, you can either make a bootable USB Flash Drive from it using tools such as Rufus or Universal USB Installer, or create a bootable DVD disc with your CD/DVD software's "Burn Image" function.
Here are Links:
Windows 7 ISO from Microsoft:
https://www.microsoft.com/en-us/softwar ... d/windows7
Linux ISO:
https://www.ubuntu.com/
https://linuxmint.com/
-- For Linux Mint, I've had better luck on "stubborn" computers with the MATE Edition (rather than the Cinnamon Edition).
Tools to create a bootable USB Flash Drive from an ISO File (both are free and Open Source):
https://rufus.akeo.ie/
https://www.pendrivelinux.com/universal ... -as-1-2-3/
-- Scroll down to "Download UUI" (about 2/3 down the page). Every once in a great while you'll get some fucking Ad with a big green "Download" or "Download Now" button, that is NOT what you want to click on!
Virtual Machines (VM) -- if you want to try Linux to see what it is like, or try/run a previous version of Windows, you don't need to Format/re-install the computer, VM software lets you do it in a Window on your Desktop without needing to erase your existing Desktop or OS:
https://www.virtualbox.org/
https://www.vmware.com/products/worksta ... ation.html
Lastly, if you need it, here are Microsoft's tools to create bootable USB Flash Drive installers for Windows 8/8.1 and 10:
https://www.microsoft.com/en-gb/softwar ... /windows10
https://www.microsoft.com/en-us/softwar ... d/windows8
https://answers.microsoft.com/en-us/win ... df465df326
Good luck. I hope things go better for you.