Microsoft has updated its Get Ready Web site to include the minimum system requirements to run Windows Vista.
A Windows Vista Capable PC must include at least a CPU running at 800MHz, 512 MB of RAM, a DirectX 9 graphics card capable of at least 800×600, a CD-ROM drive and a 20 GB HDD with at least 15 GB free for the install. Of course, systems with bare minimum specifications will be unable to run Vista in the Aero interface.
Minimum of 800 Mhz with 512MB RAM is needed for Vista
In order a PC to be certified as “Windows Vista Premium Ready,” it must have at least a 1 GHz CPU, 1 GB of RAM, a DirectX 9 graphics with a WDDM driver, 128 MB of graphics memory, Pixel Shader 2.0, DVD-ROM drive, a sound card, internet access and 40 GB of hard drive capacity with 15 GB free space.
For Windows XP, users who did not meet the minimal requirements for XP Home (300 MHz, 128 MB) were still able to install and run the operating system, albeit rather slowly. It remains to be seen if Windows Vista will allow installs on machines lesser than minimal specification.