I noticed that my computer's logic board has a red light. The characters "DS5" are written on the logic board next to the light. Sometimes I can see the light through the case when the side door is closed. What is this light's purpose?

The light indicates that the computer is on (including sleep mode), and serves as a warning that upgrades, such as installing cards or SDRAM memory, should not be performed until the system is shut down. The light does not indicate an issue of any kind.