Adobe Systems on Monday said it plans to release a Windows Vista-compatible driver for printers that use its PostScript page description language in July -- a full six months after Microsoft's new operating system was released for general sale.

PCs running Windows Vista can currently print documents on PostScript-enabled printers using a default driver that ships with Vista. But the default driver isn't capable of enabling advanced printing effects like transparencies and gradients, Adobe said.

Drivers send instructions back and forth between computers and connected peripheral devices like printers, monitors, and CD-burners.

Adobe has taken some heat from users for what they claim is its lukewarm support for Windows Vista. In March, the company made the controversial decision not to upgrade what, at the time, were the most current versions of its Photoshop, Dreamweaver, and InDesign products for full Vista compatibility.

Adobe said it was focusing its development resources on ensuring that the new CS3 versions of the products are fully compatible with the OS.

The decision led to speculation that Adobe isn't fully supporting Windows Vista because Microsoft appears to be stepping up competitive efforts against the company. Adobe recently accused Microsoft of violating European Union trade laws, claiming that Microsoft's bundling of Vista and the XML Paper Specification document creation application -- a potential competitor to Adobe Acrobat -- is anticompetitive.

Additionally, Microsoft's new Silverlight multimedia authoring tool could take market share away from Adobe's popular Flash software.

Adobe said it plans to ship its new PostScript driver for Windows Vista in July to printer manufacturers, which can then make it available to customers. The company didn't provide a reason for the six-month delay.

Adobe officials weren't immediately available for comment.