He's right. All these Genesis emulators have CD support and all of them use the ASP interface to read the CDs. When the emu tries to start up, it tries to initialize the ASPI and something is wrong with it or it is missing on your machine, you get a warning. Why the emulators do not simply disable CD support and run without it, so you could at least run ROMs is above me.
I guess it's just quick and dirty programming,
If you don't have ASPI drivers get info and the drivers here (link courtesy of the ASPI wiki page):
http://www.bitburners.com/Guides/DVD-R_and_CD-R_Recording/ASPI_driver_installation_guide/

Good luck with your emulation efforts.