The amount of conflicts varies depending on the extension being installed and what other extensions were previously installed. If you are installing the latest versions of the extension, it should be safe to select yes to all when installing.
Your configuration folder may have become corrupted. You can rename the configuration folder to have Dreamweaver recreate it. Close Dreamweaver and go to:
--C:\\Documents and Settings\\<Your User Name>\\Application Data\\Macromedia\\Dreamweaver 8
--C:\\Documents and Settings\\<Your User Name>\\Application Data\\Adobe\\Dreamweaver 9
--C:\\Documents and Settings\\<Your User Name>\\Application Data\\Adobe\\Dreamweaver CS4\\en_US
--C:\\Users\\<Your User Name>\\AppData\\Roaming\\Macromedia\\Dreamweaver 8
This will disable all the extensions in your extension manager. After doing this, can you try installing DataAssist on its own and try the wizard again?