It's ILLEGAL to rip music to a PC, even if its not shared.

Although it is legal in the United States to make backup copies of software, the legality of ripping music for personal use without the permission of the copyright holder is controversial. Historically, copying media for personal use was established to be Fair Use under U.S. Copyright by the Supreme Court in the Sony Betamax doctrine. On the other hand, the RIAA, which represents many music copyright holders has maintained that copying rights have not been granted to end users and that Fair Use does not apply.[1]

Depending on the outcome of the trial including the RIAA v. Jammie Thomas, even ripping a cd without permission from the owner of the copyright, even for personal use may be illegal. [2]

However, in oral arguments before the Supreme Court in MGM Studios, Inc. v. Grokster, Ltd., Don Verrilli, representing MGM stated:

"And let me clarify something I think is unclear from the amicus briefs. The record companies, my clients, have said, for some time now, and it's been on their Website for some time now, that it's perfectly lawful to take a CD that you've purchased, upload it onto your computer, put it onto your iPod. There is a very, very significant lawful commercial use for that device, going forward."