Have you ever received an error when opening QuickBooks?   There are many reasons why this can occur.  Regardless of the reason, there is a quick way to help you narrow down to the likely causes for launch errors.

The next time you open QuickBooks, hold down your Ctrl key.  This will suppress the last opened data file and bring you directly to the 'No Company Open' screen.  
 
If QuickBooks opens this way without any errors, then attempt to open a company data file.  If you receive the same error upon opening a data file, then the problem is in the data file itself.  
 
If you receive the error when launching QuickBooks (while holding down the Ctrl key) then the problem is most likely with the QuickBooks program installation itself and not with the data.
Use this tip to save time if you experience an error when launching QuickBooks!