A major update to Microsoft's Windows Vista operating system could leave computers vulnerable to hackers and malware as the service pack prevents several widely used antivirus programs from operating, the company said.
The list of security products that Windows Vista Service Pack 1 blocks includes Zone Alarm Security Suite 7.1, Trend Micro Internet Security 2008, and BitDefender 10. It also blocks the 2008 version of the Jiangmin antivirus product.
Microsoft said the blocks occur because the antivirus programs are not compatible with Vista SP1. "For reliability reasons, Microsoft blocks these programs from starting after you install Windows Vista SP1," the company said in a statement posted Wednesday on its support Web site.
Microsoft also said Vista SP1 prevents a small number of other programs from working properly, including Novell's ZCM Agent and The New York Times reader software.
It's not the first glitch for Windows Vista SP1. Microsoft earlier this week pulled from the Windows Update site a file that's a prerequisite to installing the service pack. The company said the file, known simply as KB937287, can cause host computers to enter an endless cycle of boots and reboots.
Also, Microsoft has delayed widespread distribution of Vista SP1 until it can resolve compatibility issues with some software drivers that control PC peripherals such as mice, keyboards, and printers.
As a result, Vista SP1 won't be available as a manual download until mid-March on Windows Update. Even then, installation will be rejected on PCs with the problem drivers. Affected users who want to access the software regardless will be able to download it directly from Microsoft.com.
Microsoft will automatically push Windows Vista SP1 to customers who have signed up for automated downloads from Windows Update starting in mid-April. Again, however, PCs that are using the incompatible drivers will be blocked from receiving it.
Windows Vista SP1 includes more than 300 hot fixes for the operating system, which Microsoft launched a year ago.
Among them: a fix for a problem in which optical disks turn blank after being formatted with Vista's Live File System; a patch for a glitch that generates an error message when large files are copied from one Vista-based computer to another over a network; and an update designed to improve Vista's speed when its operating on a computer linked to a virtual private network.