With Aero gone, the options to customize the appearance of your Windows desktop have highly decreased. Though while you don't have the option to add transparency to window borders, you can still achieve them with a simple trick (you won't have the blur anymore - just transparent borders).
To do that,
- right-click your desktop and click on Personalize.
- Activate the High Contrast White theme and
- click on the Color options beneath the theme selection pane.
- Right-click your desktop again to open another personalization window (don't close the first one).
- Activate one of the default Windows themes again.
- Afterwards, switch to the first window again -
- click the Save changes button there.
You should now have transparent window borders without blur:
As you might have noticed this way of achieving transparent borders is not intended to be used - some machines may experience graphic corruptions when using this method. If you happen to have these, you can reverse the whole thing by chosing another theme again!