You can mount drives at empty directories in other drives, just like Unix. I have C: on an SSD and mount a HDD at C:\Stuff I remember one installer that didn't

You can mount drives at empty directories in other drives, just like Unix. I have C: on an SSD and mount a HDD at C:\Stuff I remember one installer that didn't understand this (I think it was Steam) and concluded it wouldn't install to C:\Stuff\foo because there was insufficient disk space under C: - it was looking at the free space of C: (the SSD) instead of C:\Stuff . There's also plenty software out there that confuses volumes with drives and tries to enumerate the latter when it should be enumerating the former.