Me either. 3.0 was removed from my machine. I don't think we actually know which 64 bit windows OS Mountainmaster is using.
I use 64-bit Windows 7 Home Premium.
Perhaps the Prolific installer did not have 64-bit support in an early version. Lack of 64-bit support would make it behave the same as Morgan's installer. When I installed 3.0 I had a relatively recent download of Prolific's installer (November 20, 2009).
Anyway, if 3.0 is not always in the same location on a 64-bit Windows machine the new Prolific 3.1 installer had better be smart.