In this Last part of the AppCompat Series we will look at the Core OS changes which Windows 7 has undergone and how that can affect your applications. We will discuss on areas like UAC (User Account Control), WRP (Windows Resource Protection), Libraries, Removal of Live Gallery applications from the OS and the importance of porting applications for 64-bit architectures. We will also see on how these issues can be handled.

In Windows 7, the OS creates Session 0 for Services and User Mode Drivers, and creates Session 1 for first user logging in. Running services and user applications in two different Sessions avoid the security risk, because services cannot run at elevated privilege and therefore stops malicious agents. Now when we have a legacy application, in which the application which is running in Session 1 invokes a system service and waits for the user’s interaction, UI displayed by this service is not visible as it is running in a secure desktop. This article explains the Session 0 Isolation phenomenon and guidelines to mitigate the issues caused by this.

In the AppCompat series, we are looking at how to make your existing applications work on Windows 7. In previous articles, we saw mitigations on Version numbers, IE fixes and Shims etc. Now, when your application doesn’t get remediated by all these methods, you can make use of “XP Mode”. Windows XP Mode is a virtual machine package for Windows Virtual PC containing a pre-installed, licensed copy of Windows XP SP3 as its guest OS. XP Mode provides an additional layer of application compatibility in windows 7, which means that, you will have additional time to migrate your existing applications to the new operating system. In this article, you will find detailed information on XP Mode.