Two possibilities occur to me.
Part of the PC's start up routine is to test all the hardware. So you will also have a quick spin of the floppy (as long as it's enabled in the BIOS). But the "spin up" you describe would not just have started but it would have been there all the time...
More likely is that at some point you used a CD in the drive to install a program, play some music or copy over some data. You shut down the program or even the whole PC with the CD in the drive and the Registry remembers that you did so.
It should go away eventually, but if you want to hurry the process up, try retracing your actions but this time remove the CD before completely closing the application (program) and shutting down the PC.