Microsoft has published the minimum hardware requirements to run Windows Vista.

The company reveals the new specs one week before it hosts its Windows Hardware Engineering Conference (WinHEC) in Seattle. Microsoft and hardware manufacturers are expected to use WinHEC to show how Vista will run on a variety of machines, as well as showcase add-on technology built to enhance the OS.

Microsoft has outlined the requirements for running both low-end versions of Vista and higher-end versions that exploit its new Aero graphical user interface capabilities.

The company calls the former a "Windows Vista Capable PC" and the latter a "Windows Vista Premium Ready PC."

Hardware requirements for a Vista Capable PC are a modern processor with a speed of at least 800MHz, 512MB of memory and a DirectX 9 capable graphics processor.

A Premium Ready PC requires at least a 1GHz 32-bit (x86) or 64-bit (x64) processor, 1GB of system memory, 128MB of graphics memory, a 40GB hard drive with 15GB free space, a DVD-ROM drive, audio output capabilities and internet access.

It also needs a DirectX 9 class graphics processor that supports a Windows Display Driver Model Driver, Pixel Shader 2.0 in hardware and 32 bits per pixel.

The processor needs 64MB of dedicated graphics memory to support a single monitor less than 1,310,720 pixels; 128MB of graphics memory to support a single monitor at resolutions from 1,310,720 to 2,304,000 pixels; or 256MB of graphics memory to support a single monitor at resolutions higher than 2,304,000 pixels.

Microsoft began working with hardware partners several months ago to prepare customers for Vista's release. In April, PCs with stickers saying "Windows Vista Capable" became available in stores, letting customers know what hardware can be upgraded to Vista once it is available.

Microsoft is not running such a scheme to signify Windows Vista Premium Ready models.

Microsoft also stressed that purchasing a Windows Vista Capable PC does not mean customers will get discount vouchers for Windows Vista. They still must purchase an edition of the OS for full price when Vista is available.

In March, Microsoft said the consumer release of Vista would be delayed until January 2007, though business customers will have access through Microsoft volume licensing to the OS before the end of the year. Since Microsoft is missing the busy Christmas holiday shopping season with Vista's general release - which had been an important target for selling the new OS - analysts are predicting that the company may release Vista even later than January.