"Bowing to pressure from European antitrust regulators and rival security vendors, Microsoft has agreed to modify Windows Vista to better accommodate third-party security software makers. In a press conference Friday, Microsoft said it would configure Vista to let third-party anti-virus and other security software makers bypass 'PatchGuard,' a feature in 64-bit versions of Windows Vista designed to bar access to the Windows kernel.
Microsoft said it would create an API to let third-party vendors access the kernel and to disable the Windows Security Center so that users would not be prompted by multiple alerts about operating system security. In addition, Redmond said it would modify the welcome screen presented to Vista users to include links to other security software other than Microsoft's own OneCare suite. From the article: 'It looks like Microsoft was really testing the waters here, sort of pushing the limits of antitrust and decided they probably couldn't cross that line just yet.'"