The Help and Support feature stops working when Dreamweaver is configured as the default XML editor on a Windows Vista-based computer
Consider the following scenario. You install Adobe Dreamweaver on a Windows Vista-based computer. Additionally, you accept the option to make Dreamweaver the default editor for XML files. In this scenario, Windows Vista Help and Support stops working. When you try to run Windows Vista Help and Support, you receive the following error message:
Internet Explorer cannot download / from windows. Internet Explorer was not able to open this Internet site. The requested site is either unavailable or cannot be found. Please try again later.
You may also receive an error message that states that Windows Vista cannot find the file when you try to open XML files in the Windows Vista file browser.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB937491.