Preparing applications is the biggest part of any move to a new Windows operating system, especially Windows Vista. Because most organizations run up to several hundred applications on their desktops, testing and validating, repackaging and performing quality assurance on these applications requires significant effort.
With that in mind, it's no wonder people are reluctant to move to Vista. But with the release of Windows Vista Service Pack 1 in the works, more organizations will be ready to migrate to the new OS.
Preparing each application for migration can take anywhere from a day and a half to 10 days, depending on its complexity and an IT shop's familiarity with the application. If an organization is running hundreds of applications, this can add up to quite a few days of work. What's worse, this same process has to be redone every time there is a move to a new operating system.
If you're getting ready to migrate, you have to understand fully how Vista's underlying infrastructure will affect the way your applications work. For example, Microsoft has changed the version number of Windows with Vista to number 6.0. If your application verifies the version number at installation and the Vista version is not listed as acceptable, installation will fail.
Another significant change is the release of x64 versions of Vista. Although x64 versions of XP were available, more people will jump onto the x64 bandwagon with Vista because more and more hardware systems are being released with x64 processors and therefore, x64 versions of Vista
X64 versions of Windows will not support 16-bit applications. If you are moving to x64, then you will need to upgrade your 16-bit applications.
Microsoft also modified the way applications access the OS. The applications no longer have access to kernel-mode processes as they did in Windows NT and must run in user-mode only. If your applications require kernel-mode access, you will h
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ave to modify them programmatically.
The file system in Vista is also changed, which means you must update applications running at low levels of the OS — such as antivirus engines.
In addition, the Vista Web platform and the .NET Framework have been updated to new versions. Vista now runs Internet Information Services version 7, which is significantly different from previous versions because it is "componentized." In other words, you install only the components you need. All Web and ASP.NET applications that run on desktops will have to be verified.
Finally, the biggest release-related change you face is having to update Windows Installer. Because of the new User Account Control feature in Vista, applications must be trusted in order to update in user mode. Because of this, you should digitally sign your Windows Installer packages so you can then patch applications in standard user mode, which will not require elevated privileges for patching.
Use the following table to review how release-related components change how your applications will work:
[TABLE] There are other modifications that change the way Windows Installer works with packages. Because of this, you should run each of the packages you have through a compatibility checker and upgrade them to Windows Installer version 4.0.
As you can see, migrating to Vista can be a lot of work, especially in terms of application preparation. Make sure you allot enough time in your migration project timelines to adequately prepare each application.
Danielle Ruest and Nelson Ruest are IT professionals specializing in systems administration, migration planning, software management and architecture design. Danielle is a Microsoft MVP in virtualization, and Nelson is a Microsoft MVP in Windows Server. They are authors of several books about Windows and are currently working on the Definitive Guide to Vista Migration for Realtime Publishers as well as the Complete Reference to Windows Server 2008 for McGraw-Hill Osborne.
