Sustained beep ram not there

Hello, I have a problem with my computer that is related to this page however I know for a fact my ram has never been tampered with nor my computer been opened, but yet the beep is a "memory error" and when I first opened my computer there was no ram in any of the 4 slots that I have. I'm not sure if it's integrated but my computer is a desktop and I know it's not really common in desktops to be integrated but I'm just wondering if someone knows why this beep is happening?