The SVD is a small hobbyist hardware device that emulates an old floppy drive. Through an RS232 interface on your Windows or Linux box, you can download a floppy image to the SVD and then boot your favorite old program on your old machine just as if you had the floppy disk itself.  With the included software, you can easily run entire diskette images or single files such as BASIC programs.  The SVD was created originally for the TRS-80, but has expanded to include the Heathkit H8, Apple ][ and others.

The little diagram below shows the SVD connected to an Apple //+.  The SVD is depicted about twice real size. You can see the actual size of the SVD in the picture below that (the one with the cover off of the SVD - that's my hand).