T400 and Windows 10

[bblumberg]

Hi everyone,

I thought I'd share my experiences with installing Windows 10 on my old T400 which was happily running Windows 7. I tried the automatic updating process many times from the web, from a USB stick and finally attempting a clean install from a USB stick. All Lenovo software had been deleted, but to no avail. I gave up and left Windows 7 installed. However, after a successful clean install of Windows 10 onto a Windows 10 updated T420, I decided to try again.

Following advice in the T500 Windows 10 thread, I turned off the security chip in the BIOS, disabled switchable graphics (I use the integrated graphics anyway) and set the disk interface from AHCI to compatibility mode. I then did a clean install of Windows 10 and, voila, it worked. However, since this was a clean install, rather than an upgrade, I was unable to get Windows 10 to activate. After a few days of waiting for activation to take place, I restored Windows 7 from a backup and found that it would not boot. I went back into the BIOS and set the disk back to AHCI and Windows 7 booted. Then I tried an upgrade to Windows 10 and it worked flawlessly. Then to get a fully clean system, I just did a clean install of Windows 10 and it worked again so AHCI was not the issue. Therefore, at least for me, disabling the security chip and switchable graphics made the difference. At this moment, I am reinstalling the software I use and this machine should continue to be a serviceable backup for some time to come.

Bruce

[RealBlackStuff]

You need to update a machine from W7/SP1 or W8.1 to W10 first, to get registered with Micro$haft.
After that you can do a clean install from scratch any time in the future, or go back to your old OS.

You should perhaps do that before July 29/2016 with every machine you intend to keep.