The only DDE I am aware of in Windows is Dynamic Data Exchange.
This was where you could link two application together so that info from one would be updated by info from another.
So you could have an Excel spreadsheet and link that Excel spreadsheet via DDE to Word, so the spreadsheet would appear inside Word.
If you were in Word, and the data in the Excel spreadsheet was updated, the image in the Word document would also update.
Although this is no longer used the technology is still in Windows XP.
Are you doing anything like that ? Maybe usign an old version of MS Office ?
More details here
http://en.wikipedia.org/wiki/Dynamic_Data_Exch ange
(There could be another DDE but I can find no reference to it in Google)