A cooling system is used to cool heat generating devices within a personal computer. The cooling system has a first fluid loop and an expandable array of one or more second fluid loops. For each of the second fluid loops, heat generating devices transfer heat to fluid flowing through corresponding heat exchanging devices in the loop. Heat is transferred from the fluid in each second fluid loop to a thermal bus of the first fluid loop via a thermal interface. The second fluid loop can be a pumped fluid loop or can include a heat pipe. Within the first fluid loop, a fluid is continuously pumped from the thermal bus to a fluid-to-air heat exchanging system and back to the thermal bus. Heat transferred to the thermal bus from the first fluid loop is transferred to the fluid in the second fluid loop passing through the thermal bus. The heated fluid is pumped through the fluid-to-air heat exchanging system where the heat is transferred from the fluid to the ambient. The thermal bus provides a modular, scalable cooling system which allows for the expansion of cooling capacity without breaking the fluid lines.