I previously used a Dell Dimension XPS D300 running Windows 2000 Professional (and Windows NT before that). I bought the Dell in 1998, and it is still a fine machine, although a 300 MHz Pentium II is well slower than what's available today. The Dimension series gives great value, and if you choose the right video card (the Matrox Millennium at that time), the base machine can run Linux as well as Windows. Dell will also configure a Linux PC for you, but I thought this service was unreasonably expensive last time I checked.