My success story upgrading to Windows 10 on a Toshiba Satellite L305D-S5974 from Windows 7 Professional. Initially (when click on the Windows 10 upgrade icon on the task bar) I got the message "Unfortunately, this PC is unable to run Windows 10" with the
stated compatibility issue: "ATI Radeon X1200 Series - The display manufacturer hasn't made your display compatible with Windows 10". I then burned a DVD with the Windows 10 Media Creation Tool (make sure you choose the one matching your current OS - 32 or
64 bit, Home Edition or Professional etc. ) and ran the upgrade on the laptop without any issues at all, ending with a running and activated Windows 10 Pro. The display driver was the basic Microsoft so the Power option was missing the "Sleep" option. I went
to toshiba.com web site and found, in the support section, the downloads for my laptop model. I tried to install the display driver from there but when running the downloaded file nothing was happening, except a brief icon showing on the task bar, but without
the normal installation dialog. Thinking that I did not download the right driver I ended by downloading and running several versions. All of them were behaving the same ending without upgrading the basic Microsoft driver. I then read more through the posts
in this thread and found and did myself this: open the Device Manager, go to the display node, choose to update the driver and choose the option to search on your laptop (not on the internet) and set the search to look starting at the root of the C:// and
include sub-folders (since I don't know where exactly the driver is located). This worked for me and the display driver now shows:
ATI Radeon X1200 Series
Driver Provider: ATI Technologies Inc.
Driver Date: 12/1/2008
Driver Version: 8.561.0.0
Digital Signer: Microsoft Windows Hardware Publisher
Not sure if the driver that was eventually found and installed is one of those that I have downloaded from toshiba.com or maybe the old driver that was left behind by the upgraded OS.