If memory serves me correctly, it IS the "C" Key. You may just have to zap the PRAM a couple times, then nail the "C" key after you hear the ROM tone.

It was on older machines that you had the archaic boot combinations.
MacBook 2GHz Intel Core 2 Duo w/ 2GB DDR2 RAM & 120GB SATA 5400RPM HDD
Canon Rebel XTI
Google Cr-48 Beta Laptop