Windows Vista by default has huge borders, probably to show off the new transparancy. If you'd prefer a more slimmed-down, minimal approach, you can easily configure this setting to make it more reasonable.

Here's the normal window border, that you are probably used to. The borders look even more ridiculously large if you aren't using Aero.

And here's the window border after we've removed the padding. Much less wasted space!

To make this change, we'll need open the classic Appearance Settings dialog. Right click on the desktop and choose Personalize. Then click on Window Color and Appearance:

If you have Aero enabled, you’ll have to click on “Open classic appearance properties for more color options”.

Click the Advanced button, and then change the dropdown to Border Padding. The default will be set to 4. I changed mine down to zero for the second screenshot above.

A setting of 1 or 2 would probably be more reasonable for your system. You'll have to test it out and see what you like best.