Well this issue has been a long problem for me. I am using PostgreSQL 9.5 (x64) on Windows 7 Enterprise (x64) and I have been running into problems when I try to run create extension plr;. I used this link to donwload plr for windows. Copied all the files to respective directories. Added environment variables, but when I try to to run above command I get this error:
ERROR: could not load library "~/PostgreSQL/9.5/lib/plr.dll": The specified module could not be found.
But, .dll file is present in the directory. I would be thankful if someone could help me to resolve this problem?
Have you restarted postgresql service after adding environment variables? I don't know about windows 7, but it should be somewhere in control panel -> administrative tools (or something like that). Find service named "postgresqlXXX" and restart it.