Wrong!!! Dell does support XP. Go to the Dell site, locate your PC, select downloads. Then select the operating system - XP.
Meanwhile I have a crazy problem. I had the HDMI working flawlessly - with no special accomadation. Then I had to do a new install of Windows XP Professional , SP3 (as before). Now it works with all kinds of smudges, shadows, etc. I paid to have all my drivers updated - still the same problem. I have yet to find a solution.