How to Close Applications in Windows Vista
Closing the programs that you're not using in Windows Vista frees up system memory, helping Windows Vista to run faster. Too many open programs can make other functions, such as printing, saving, and moving between applications, take much longer. So, if you're not using an application, exit of that application using the following steps. Vista will thank you.
Save any open documents.
If there is a document open that you haven’t saved, you see a dialog box asking whether you want to save the document. Click Yes or No, depending on whether you want to save your changes.
Close any open documents using one of three methods.
Click the Close button in the upper-right corner of the window; click Alt+F4 to close most open windows; or choose File→Exit.