Dell XPS 400 is a desktop PC released in 2005, and Dell officially only supports for it Windows XP (32-bit and x64), and Windows Vista 32-bit. I installed Windows 7 64-bit anyway on it, and it is able to detect and install most of the devices, including display adaptor RADEON X600, in the old PC. The only exceptions are the Ethernet LAN card and Wi-Fi card. Windows 7 x64 complains it could not find the driver for the LAN network device. It seems that it could not even see the wireless adaptor.