As some of you know, if you mount a harddisk image file that has a real working dos installed on it in dosbox, and then boot it, dosbox will boot a real dos, like Bochs.

I have MS-DOS 6.22 installed on a 300 MB image file. I had 69 MBs of space left on it, and decided to try using drivespace, to see whether it works.

The results were marvelous, not only did it work, like it did on a real computer, but after drive space I had 279MBs of free space left.
And since smartdrive isn't compatible with drivespace, I deactivated the smartdrive driver in config.sys so there's no noticeable loss in free conventional memory.

Of course, there's a disadvantage: You can't directly copy files with winimage to the compressed drive. You either have to copy it to the "H" drive that remains uncompressed and contains the data of the compressed drive in one file, or create a new small harddisk image, copy things on it, then mount it in dosbox as a secondary harddisk, and after this, copy the files from these drives to the C drive.

And last but not least, the size of the image file itself remained 300MB!