Failing the ability of the PC to talk to the web cam, you likely will need to upgrade to a processor that can handle live video feeds. Presumably ARM processors (mbed, beaglebone, raspberry-pi, etc.) have enough memory and processor speed to handle it, but I don't know from personal experience.
If you just need to overlay some simple text over the video feed, you could use a video shield such as http://nootropicdesign.com/ve/
, and then have the PC accept composite video input, possibly through a TV card or frame grabber.