All windows in Vista have thick borders. Transparency shows off quite well on them. But if you don’t like such thick borders, and would like to reduce or trim them follow this procedure
First you need to right-click on Desktop and open select Personalize.
Click on Windows Color & Appearance.
Here click on Open Classic Appearance Properties.
In the new dialog box select Advanced.
Again a new dialog box will open. Here from the “Item’ drop down menu, select Border Padding. Change the default value from 4 to say, 1 and click ok 2 times.
That’s it enjoy your new vista borders.