Windows XP/2000 - Computer is Loud posted in the Operating Systems forums; After I leave my computer on for a few hours it becomes really loud. What is wrong and is there a way to fix this?...
You may have a thermostatically controlled fan in there. As the heat inside rises, so does the RPM of the fan. Try running the PC with the case open for a while and try to pinpoint the exact location of the noise when it occurs.