sargan said:
If I take for example and mpeg file ... if it is on C drive and I double click it, it opens fine with the player VLC (set in Ctl Panel > default programs > set associations)

If the file is on the drive where I moved the 'my video, my documents etc to' .. i.e D:\ it does not open ... just pop up error of "This file does not have a programme associated with it ....."
If I right_click and use 'open with' it will run OK
If I move file to C:\ it runs by double clicking fine.

Is there a known issue here ?
Is there a way of forcing associations to be same across both HDD ?
I have never seen this issue.

After I install an OS I set WMP as the default player.

Then I install VLC at all defaults which seems to only open those files that WMP cannot play.

Then I install QuickTime which opens only its files such as .mov which will play sideways if not played by QT.

I have never had these change on me, but if they did I would in Control Panel>Defaults set VLC as Default, and then for Apple movies and pictures manually set QT under file associations there.

Any variance from this on a different drive letter where the User folder has been moved would seem to me to be corruption and not having at all to do with the function of moving User folders which I have done for years with no issues whatsoever.

You can read here how I root my User folders in Skydrive to Sync, Backup and Store your Files to the Cloud with OneDrive .

What I would do is reset an affected User folder to default to see how it changes, then move it back again.