I'm trying to go back to playing Fallout 3 on the same computer I've always played it on and I'm getting the Securom 'Emulation detected error (e.g. 2500)'

I followed the link to

"A: Please unmount all images, deactivate running emulation software and put the original disc in your drive.
If the error message persists, please download the SecuROM? Diagnostics Tool and follow the instructions on the website."

Please tell me what is meant by 'all images' and "emulation software." I am using the original disk from the GOTY edition and as far as I can see, I'm do not have 'images' or 'emulation software' running.
what is meant by these things? I'll get rid of them if they're on, but I certain didn't put them on (unless a trogan of some sort loaded them.)

I downloaded the diagnostic tool and ran it but all that did was give me the 'Emulation detected error (e.g. 2500)' which did not tell me what I need to do to be able to play the game again.