"Part of this is perception based on fact - Windows Vista is built on a new architecture that promises tightened security and reliability. Consequently, the applications that ride on top of Windows Vista need to communicate with the kernel in different ways. So what has helped fuel current perception around application compatibility? Why did many applications 'break' in the migration from Windows XP to Windows Vista?" Microsoft asked rhetorically.

And it seems that application compatibility issues consistently point to a single culprit: User Account Control. The watch dog Microsoft introduced in order to train both end users and developers to utilize and respectively build applications running with standard privileges for security reasons has come back to bite Vista uptake.

"Standard user mode limits file and registry access by applications on the computer. User Account Control exposes non-compliant actions, with permission prompts to standard and administrator users. Changes in permissions will cause most of the issues with earlier versions of applications, where administrative access was assumed during development and testing," Microsoft explained revealing the first reason for Vista application incompatibilities.

But two additional sources of compatibility problems are also connected with the UAC. Microsoft pointed to Internet Explorer 7 Protect Mode killing web-based applications as well as the Windows Resource Protection preventing programs to writing to protected areas of the operating system. In the end, the Redmond company traded flexibility for security, and legacy applications tailored to Windows XP running with administrative privileges bit the dust.

Additionally, Microsoft informed that "operating system and browser version numbers change with each release, which might cause issues with applications that check for a specific version number upon installation. Application shims are available to fool the application into thinking the operating system or browser is the application-required version."

And on top of it, the new driver model introduced in Vista, that enables the eye candy Aero graphical user interface, along with undocumented APIs, also caused compatibility issues. Over a year since Vista hit the shelves, the Redmond company claims that the operating system benefits from in excess of 15,000 signed devices and components and the advances brought on by Service Pack 1. In this context, Microsoft is not shy to put forward an invitation to give Vista, now with SP1, another try.