It seemed like a simple task:
- Download Windows 10 image from Visual Studio subscription.
- Extract installation files to USB stick.
- Boot ThinkPad on USB stick.
- Install Windows 10.
The installation set is not specially large and fits easily on a medium (8 GiB) USB stick.
But the file "install.wim" is larger than 4 GiB in the latest Windows 10 image. And when a USB usually is formatted with FAT32, it can't hold a file larger than 4 GiB.
My first thought was to format the USB stick with exFAT, but the T440s couldn't boot on the USB stick with the installed BIOS level.
My solution was:
- Format the USB stick with FAT32.
- Download the RTM image of Windows 10 where the file "install.wim" is smaller than 4 GiB.
- Extract installation files to the USB stick.
- Boot the ThinkPad on the USB stick.
- Install Windows 10 RTM.
- Update Windows 10 to current release - with several reboots.
If I meet that challenge then I will update this post.