What is the $WINDOWS.`BT folder? Is it safe to delete?

Hi Lam

Open the Settings App (gear icon on your Start Menu)

Go to Update and Security - Windows Updates

What update(s) are showing as pending on your system?

if you are seeing a Feature Update like version 1809 or 1903 in that list, then most likely the files being downloaded fro that update are in the $WINDOWS.`BT folder

Otherwise, you can safely delete that folder, run Disk Cleanup twice as explained below, then after that, if that folder still exists, try deleting it manually . .

Before proceeding, if you have any files in your Downloads folder that you need to keep, move those to another folder for long term storage . . .

Open File Explorer
Click on your hard drive
On the Manage Tab, click Cleanup
Let Disk Cleanup do its initial scan
Select Everything in the list and choose Delete

Start Disk Cleanup again
Let Disk Cleanup do its initial scan
This time in the resulting dialog, click 'Cleanup System Files'
Let Disk Cleanup run another scan
Select Everything in the list and choose Delete

If it is a large folder, then you have a feature update waiting to install. If it's a small folder, then it's a remnant of a recent feature upgrade.

In either case it's safe to delete but if it's before the upgrade, the next time you reboot your computer, the upgrade will fail and have to redownload the feature update.