My friend can't install DMD 2.076.0 after he deleted contents of C:\D

[Enjoys Math]

Series of messages from installer:

DMD v2.076.0 is installed on your system
Press 'OK' to replace by DMD 2.076.0
An error occurred when removing DMD v2.076.0
Run 'dmd-2.076.0.exe /f to force install

And using the command line has no effect - it repeats the above.

He got into this situation by accidentally installing Visual 
Studio and / or Visual D to C:\D where I told him to install D to.

At one point I told him to delete everything in C:\D and start 
over.  *That* was a mistake...

He's used a trial version of Revo-Uninstaller to remove contents 
of registry.  The issue remains.  How can we repair his system so 
that we can install D on it again?

Thanks.