I had this problem because my BIOS was telling windows there was supposed to be a floppy drive, when actually I don't have one installed.
It's pretty easy to tell if this is the case for you by going to your Computer and checking the drives listed there - if there's an A: drive showing up, but your PC doesn't actually have a device to put floppies in anywhere, then the best thing to do is go into the BIOS and disable it (since you don't have it anyway, there's no reason to tell windows it's there

).
To do this just tap the DEL key (or other key as listed on your motherboard's startup screen) while the computer is booting up. In the blue BIOS screen, select advanced CMOS features, find the floppy drive entry and change it to "none". Now exit & save Y -> restart and voila, the floppy drive is gone and DA2 should stop complaining about it.
If you do actually physically have a floppy drive installed and it's giving this error it's best to disable it through device manager.
If you don't have a floppy drive showing and still get this error, check that you aren't running any virtual drive software like Daemon Tools, etc. If you are, then start the virtual drive manager and disable all virtual drives first, before shutting down the program.