I have a T400 which runs Windows 10, build 1903. A lot of the time there is artifacting or random lines or squares glitched on the screen, and when i move my mouse over it it fixes, which makes me believe its a VRAM issue or something. After a lot of graphics change (like opening Chrome) then more artifacting appears all at once until I move my mouse to fix it.
The problem persists when I use the VGA port and an external monitor - when duplicating the screen I can see the artifacting on the external monitor too.
I booted into Linux Mint 19.3 for a bit (with and without the external monitor) and didn't see any corruption, but in any case i'd like to know if its a hardware or software issue, and if anyone has had this issue before.
EDIT: To anyone who comes across this, I did not solve the issue, and ended up using Linux Mint 19.3 all the time as this doesn't occur on Linux. I suggest you use some flavor/distribution of Linux instead of using an earlier, supported Windows (assuming its a windows graphic driver issue and not hardware related) simply due to security vulnerabilities.