I just installed MinGW and it all seems to be working.

However I do prefer to keep all my own work well away from the C:
drive as that makes life much easier when doing backups and upgrades.

Is there any way to make msys point my "home" folder to the D: drive?

Add an entry to MSYS/1.0/etc/fstab like this, where YourUserName is the value of $LOGNAME:
D:/YourHome  /home/YourUserName

This should work too, it's what I use here:
C:/Users  /home