www.lutron.com/PasswordProtectedDocumentLibrary/HWQS%20System%20Requirements.pdf
You may have to sign in to your myLutron account to view the file.
If you are thinking MAC, one thing the document omits is that, even running windows, the MAC OS handles the external communication. MAC OS natively blocks FTP which Lutron uses. You will need to adjust some settings to make that work.
RR2 takes some time to load and you can't have RR2 and HQS open at the same time <grumble...grumble...>. Compiling also takes a lot of resources. If you are not compiling and don't have to swap between RR2 and HQS, the desktop may be fine.