There are several ways to break the DRM (Digital Rights Management) on "secure" MS Reader .LIT files, for example ConvertLIT will do this. Once you have a .LIT without DRM it can be converted to any device, for example lit2prs
will do this for the Sony. Keep the DRM-free .LIT as your "archive" version, and you are future-proof. Note that format shifting is generally considered "fair use", but breaking DRM (even for fair use purposes) is not legal in some places.