Sass is compatible with Ruby 2 as of version 3.1.18, so that shouldn't be an issue.
I just tried installing it on my Win 8 box which is running 1.9.3:
ruby 1.9.3p429 (2013-05-15) [i386-mingw32]
C:\\Users\\Pullo>gem install sass
Fetching: sass-3.2.10.gem (100%)
Successfully installed sass-3.2.10
Installing ri documentation for sass-3.2.10
1 gem installed
What is the exact error message you are getting when you try to install the gem?