Certain online games are not compatible with Microsoft's latest operating system, according to the CEO of the largest online gaming company.

SLIDESHOW: Look Inside Windows Vista

WildTangent CEO Alex St. John said more than 500 of the web's most popular games do not work with Vista.

"The new Vista operating system has pretty extensive incompatibilities with a lot of popular casual games," St. John said.

More than five years in the making, Vista was released for business customers Nov. 30, but the new Windows operating system's unveiling for consumer buyers was scheduled for Tuesday around the world.

For Vista, the problem is more than just growing pains. The company took careful steps to make the new operating system as secure as possible, but those steps are also preventing consumers from downloading some web content, including casual games.

"Real Arcade, Yahoo, AOL and interestingly Microsoft's own casual game download site is largely broken with Vista, and will take some time to fix," St. John said.

New PCs from Dell, HP, Gateway and Toshiba will include fix-it software from WildTangent, but consumers buying the stand-alone software will be out of luck.

"It is pretty staggering to think about it," St. John said.

Support.com chief software officer Cadir Lee said a recent study done by his site showed that 77 percent of people were worried about upgrading or migrating.

"You'd think a brand new machine would be worry-free," Lee said.

In Tokyo, about 80 people lined up at the Bic Camera Department Store to become among the world's first consumers to own Vista. Celebrities and executives were on hand as a large-screen television set displayed a countdown to the midnight launch (10 a.m. EST).

The Redmond, Wash.-based software maker contends that Vista is such a huge improvement over previous computing platforms that users inevitably say "Wow" when they see it -- and so the word plays a big role in the company's marketing campaign.

When users boot up Vista for the first time, they'll be wowed by the slick 3-D graphical user interface and document icons that give at-a-glance previews, Gates said. The next wow comes when they start using a system-wide search program that Microsoft's engineers built into both the operating system and new versions of Microsoft Word, Excel and other Office 2007 elements, which also hit store shelves at midnight.

Microsoft shares dropped 20 cents to $30.40 in late morning trading Monday on the Nasdaq Stock Market.