For Advanced users only or experimenters in windows.
Not to sure of implications but I have 3 Yacy's running on my P4 at the same time with different roles.
Install YaCy into a separate directory.
Start Yacy > change port number eg 8095
Rename icon eg YaCy 8095.
Install YaCy into a another directory.
Start Yacy > change port number eg 8100
Rename icon eg YaCy 8100.
The second install of YaCy wont start if the default port 8090 is being used.