if you have a backup of the reaper project file and the corresponding audio files you should be good to go. if you use any midi tracks, the default setting has the midi info stored in the project file itself, so no worries there. however on a new hard drive you'll probably have to reinstall any third party plugin you might have been using in your projects. if reaper doesn't find your plugins it will leave them offline (and preserve their settings) until they are available again.