I'm reporting my experience with PowerDirector 10 and ImgBurn 2.5.7 running under Windows 7 Pro x64.
When you use PowerDirector to burn to an AVCHD folder you will get the folder structure
NameYouGiveToBurnedVideo
---My Video
------BDMV
---------BACKUP
---------CLIPINF
---------PLAYLIST
---------STREAM
Note that Powerdirector inserts the intermediary folder My Video under whatever name you told it to use for your output folder.
Point ImgBurn at the My Video folder, not at the NameYouGiveToBurnedVideo. ImgBurn only looks one level down for the content folders.
If ImgBurn is set to burn a DVD when you point it to an AVCHD or Blu-Ray folder output by PowerDirector, then ImgBurn will display a message "Your image contains a 'BDMV' folder in the root directory so I'm going to assume it's a Blu-ray Video disc.
...
Would you like me to adjust the setting for you?
Click Yes and ImgBurn will proceed in an obvious way.
You then burn an AVCHD DVD disc.
Note that the AVCHD DVD disc will play only in a Blu-Ray player, not in a standard DVD player.
Note that you do not need to tell ImgBurn what kind of disc you are burning. It figures that out from the folder structure. If your next project is a standard DVD and you point ImgBurn at a standard DVD folder created by PowerDirector and ImgBurn is set to burn a Blu-Ray or AVCHD, then ImgBurn will warn you about that situation and offer to change its settings back to DVD. ImgBurn is very forgiving, which is what makes it possible for me to use it.