"We play by the same rules with our own products," Toulouse said. "Nobody patches the kernel."

Toulouse also downplayed the impact of Patchguard, saying that adoption of 64 bit Vista would be slow, given that fewer applications have been written to run on it, and the 32-bit version of Vista runs on new, 64-bit platforms.

On other security features, such as the Windows Security Center user interface, Microsoft allows ISVs to use the features or ignore them. The company has also made it easy for competitors to turn off default security features like the Windows Defender anti-spyware product and Vista desktop firewall silently during installation, Toulouse said.

Microsoft has made great efforts to give third party vendors such as Symantec access to Vista, such as giving Symantec employees office space at the company's Redmond, Washington, headquarters and access to Vista source code and builds, Toulouse said.

The EC isn't opposed to Microsoft improving the security of Vista, but believes that there needs to be diversity in the security market to stimulate innovation, Todd said.