SharePoint 2007 error while opening the site in designer - this website has been configured to disallow editing with SharePoint designer

One my client having SharePoint 2007 environment. We got some requirement to check the existing functionality in one of the site. To verify the existing web parts I have tried to open the page in SharePoint designer. 

While opening the site in SharePoint designer 2007, I got the error saying as “This website has been configured to disallow editing with SharePoint designer.”I am having Site Collection Admin privileges over the site and having Farm Admin credentials on the server.

In my current site designer settings are disabled. In SharePoint 2013/2010 environments we can enable designer settings through SharePoint central Administration. But in SharePoint 2007 we have to enable through onet.xml file located in file system 12 hive.

To enable designer settings, Navigate to 12 hive templates folder located in C:\Program Files\Common Files\Microsoft Shared\Web Server Extentsions\12\Template\SiteTemplates \XML , (Here Site Templates is generic folder, Depending on site template we have to choose the folder)

Select  Onet.xml, Open it with any text editor. Check for “<Project Title” tag and Remove “DisableWebDesignFeatures=wdfopensite” text. Save Onet.xml file and Reset IIS by running IISRESET command.

By removing the text from Onet.xml file we can enable editing through designer. But to update this change in Onet.xml file we need to have farm admin permissions on the farm.

Hope this helps.