Well, you got a few options.
1. Go wireless (Get a wireless router, connect it to your PC if it has wifi connectivity, if the PC doesn't have a wireless card, get a wifi USB adapter)
2. Powerline (still wire, but only requires a power hub from your wall)
I am not sure how #2 works, so here's a link that might help you: http://en.wikipedia.org/wiki/Power_line_communication
If you don't want these options above, then connecting your modem to your PC for 30 feets away is probably your only option.