I stand corrected.
After doing some research, it appears that no matter how one wishes to rationalize their actions, it is clearly a violation of applicable law to possess a copy without also possessing the original, and might even be illegal to have a digital copy for personal use even if you do have the original. Even though the courts have ruled that a cassette copy of materials you own is fair use, there has never been a similar ruling concerning digital copies. The RIAA still contends that any digital copies (cdr or hard drive) for any reason are illegal, but so far they have only prosecuted individuals sharing files, and not those copying for personal use.
After doing some research, it appears that no matter how one wishes to rationalize their actions, it is clearly a violation of applicable law to possess a copy without also possessing the original, and might even be illegal to have a digital copy for personal use even if you do have the original. Even though the courts have ruled that a cassette copy of materials you own is fair use, there has never been a similar ruling concerning digital copies. The RIAA still contends that any digital copies (cdr or hard drive) for any reason are illegal, but so far they have only prosecuted individuals sharing files, and not those copying for personal use.