3.) Mount the Towns System Software V2.1L51 CD image. You have to convert the original bootable CD image to CHD before.
4.) Start The FM-Towns emulation (MESS).
5.) You will see now the following screen (the drive letters can be depent of the current CMOS RAM):
6.) As first we have to create a partition (HDD label, OS type, assigned space, setting as active).
7.) Choose the option " " (3rd blue field, 3rd option)
8.) You will see now the following screen:
9.) a) Click in the first field and type HDD (as example) for the label and OK. b) Choose FM-OASYS and OK c) Assign the space (as example: 127MB) and OK. d) Make the partition active. Click on the first box to be black.
10.) Close now the partition window.
11.) As next we have to assign a drive letter to the partition.
12.) Choose the option " " (3rd blue field, 2nd option)
13.) Click on the first HD symbol  and choose the 1st option.
14.) You will see the drive letter D beside the HD symbol.
15.) The Harddisk image is now initialized. Close the window.
16. Open the Tools folder
17.) Click on the HD Installer symbol to install TownsOS and to make the Harddisk image bootable.