In order to validate QB(XML) for integrating QuickBooks you need to download the most recent SDK at:
 
You must be a registered user of Intuit to download the SDK.
 
About the SDK:
 
Although the Intuit Partner Platform (IPP) is the preferred pathway for developing Software as a Service (SaaS) applications that integrate QuickBooks data, we continue to support the QuickBooks Software Development Kit for desktop and custom applications. The QuickBooks Software Development Kit (SDK) allows you to develop desktop software solutions that integrate with QuickBooks--the most common small-business accounting platform.