Do you need to buy new hardware for running Windows Vista? As I'm not a subject matter expert on this, I'm going to stick with the details of my own experience with my 2 year old home desktop computer that is running Windows Vista beta 2 and Office 2007 beta 2.
It's an HP Workstation xw5000 machine with some good extentions, such as a Hercules graphics adaptor (ATI Radeon 9800XT) and a SATA hard disk. Although this machine is more than 2 years old, it runs Windows Vista beta 2 and Office 2007 beta 2 extremely smooth. Installation was a breeze and Windows Vista Aero was enabled by default. Here is a screenshot of Windows Vista's Performance Rating of this machine:

Windows Vista's performance rating of my HP Workstation xw500.
Just in case you want to know, we've put up a page that gives an overview of when a PC is Windows Vista Capable or Premium Ready. You can also have a look at the minimum system requirements for Windows Vista.
Tags: Microsoft Windows Windows Vista