In the fun, but mostly useless, knowledge category, tonight I loaded MS-DOS 6.22 onto Parallels. I didn't have a copy on CD, only floppies and I couldn't get Parallels to see the USB floppy, but I was able to easily make floppy disk images of the originals and mount those. Here's how:

• Plug in the USB floppy drive and load the floppy. You should be able to see all the files from the Mac Finder window.
• Start OS X's Disk Utility application. Click on the floppy and then click "New Image" in the menu bar of Disk Utility.
• Select "Read/Write" for image format and no encryption.
• Type a name and then click save.
• Once the image is done, change the extension to "fdd". I did this in Terminal so that I didn't have to put up with Finder asking me insipid questions.

That's it. Now you've got an image that you can mount from any Parallels instance. I created images of the four original MS DOS 6.22 install floppies and in a few minutes had a working instance of DOS. I even fired up BASIC and played with it a bit. I'd forgotten about "DoubleSpace" and other programs for making the computer usable. DoubleSpace seems downright laughable in this day with 200Gb drives in a laptop, but there was a time...