As your data file grows larger some reports and processes may begin to run slower. One way to make QuickBooks more efficient is to set user preferences to clear all open windows each time you exit QuickBooks.

To change the default setting for each user go to
 
EDIT>PREFERENCES>DESKTOP VIEW and check the radio button that reads "Don't save the desktop"
 
If you save the desktop, QuickBooks will reopen every window you had open in your previous session at the time you exited QuickBooks.  This includes any reports you had open that may require a tremendous amount of QuickBooks resources to generate a second time.