1. Open an elevated-privilege Command Prompt window(as administrator),
2. At the Vista Command Prompt, type wmic and press ENTER,
3. Click the Maximize Window button of the Command Prompt window (the middle button at the upper-right corner) to maximize it,
4. Type exit and press ENTER,
5. Right-click the Vista Command Prompt Title-bar and select Properties option menu,
6. Without changing anything, click OK button to close the Command Prompt Properties dialog box,
7. Type exit and press ENTER to close the current Vista Command Prompt.
8. Now, re-open the Vista Command Prompt window again (as in step 1), it should have automatically and fully maximized to fit your Desktop resolution! I tested it successfully in Windows Vista Ultimate, and I suppose this tricks will works on other Windows Vista editions as well!
You may also manually configure or set the window size of Vista Command Prompt, via its Properties dialog box, in the Window Size of Layout tab. Though, that’s trivial to configure both the width and height value for different Desktop resolution!