"Because Vista is such a major overhaul to the Windows operating system, Check Point is busy in development efforts to ensure that new Vista-compatible versions of ZoneAlarm will live up to high standards of protection," said a spokeswoman for the company, which is based in Ramat Gan, Israel, and has its U.S. headquarters in Redwood City, Calif.

Check Point expects to release a Vista-compatible update in a few months, the spokeswoman said. But, she added, some of the features in the new version may differ from Check Point's current release "due to the different needs and functionality" in Vista.

F-Secure Corp. expects to release a Vista version of its flagship Anti-Virus 2007 software in May. Par Andler, a spokesman at Helsinki, Finland-based F-Secure, said the product is arriving later than Vista itself did because the company wants to make sure it gets enough customer feedback on a beta version of the antivirus tool.

"As the volume of Vista installations worldwide has been very low so far, it has been difficult for any vendor to ensure a high enough volume of external technology-review testers," Andler said. He added that F-Secure thinks it can complete a sufficient level of testing during the spring.

Even top vendors like Symantec are admitting to some difficulties. Symantec has ported its most popular products, including Norton AntiVirus and Norton Internet Security, to Vista. On Tuesday, the company also released a new bundle called Norton 360 that combines its security and data backup tools and runs on both Vista and Windows XP.