You can install LispWorks 6.1 in the same location as LispWorks 6.0 or previous versions. If you always choose the default install location, a new
LispWorks 6.1
folder will be created alongside the other versions.
Similarly LispWorks Personal Edition 6.1 can be installed in the same location as previous versions.
LispWorks Release Notes and Installation Guide - 23 Dec 2011