Where do I start?

When you work on a given subject for a while, you tend to jump right in and forget to start at the beginning.   In the Application Compatibility lab, we kick off the week with an overview presentation and cover the basics of common compatibility issues.  Those topics are probably a good place to start with this blog.

The first thing to mention is the Application Compatibility CookbookThis is the primer of Application Compatibility.  I was going to call it the K&R of of Application Compatibility but I don’t want to date myself ;-).  I highly recommend reading the cookbook or at least keep it handy for a reference.

Now that you’ve looked at the cookbook (Go look at it now if you haven’t), you are probably saying, “Whew, that’s a lot of stuff.  Can you just tell me the top issues with Application Compatibility?”  So, let’s start with a list of the top areas of issues:

User Account Control (UAC):

UAC is intended to run applications as standard user by default.  Even if you are a member of the administrators group, applications that are not marked to run with administrator privileges will run with reduced “standard user” rights.  Applications may not be designed to run as a standard user and may not have rights or privileges to certain resources.

Next steps if you have an issue:


Installation issues usually revolve around UAC.  Almost all installers need to run with admin rights because they usually write to Program Files or HKLM in the registry.  MSI issues usually revolve around custom actions being run in the wrong context (user or admin).

Next steps if you have an issue:

Service Isolation

On Vista and Windows Server 2008, only services run in session 0.  Desktop applications run in sessions 1+n.  This blocks Windows messages between services and desktop apps.  This also blocks services from displaying UI on the desktop.

Next steps if you have and issue:

Internet Explorer Protected Mode

IE in protected mode is sometimes called “Low Rights IE”.  When protected mode is on, IE runs at a low integrity level.  This isolates IE from the rest of the processes and resources on the system.  ActiveX controls and browser objects may not have appropriate rights running in protected mode.

Next steps if you have an issue:

That’s it for now.  One final note, the area for all things regarding Application Compatibility can be found on Technet.


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