You don't need to install anything. Workbench can as well be run from Floppy disk.
You say you have all five Workbench disks, but the Install disk with HDToolbox is missing.
So you should download these files:
http://www.aminet.net/search.php?query=hdinst.lhahttp://www.aminet.net/search.php?query=RDBrecov.lhahttp://www.aminet.net/search.php?query=lha.run- Enable the write protection on all your original disks.
- Boot from the Workbench disk.
- Insert the Storage disk, open Storage, open DosDrivers and doubleclick PC1. (If there is no PC1 in Storage/DosDrivers, click PC0 once and choose "copy" from the menu. Click "copy of PC1" once and choose "Rename" from the menu. Rename it to PC1. Click PC1 once and choose "Information" from the menu. If there is a tooltype reading UNIT=0, change it to UNIT=1. If there is no unit tooltype, add one reading UNIT=1. If there are brackets around the tooltype, remove them.)
- You are asked to insert the Workbench disk. Do so.
- Now insert an empty floppy disk. An icon PC1:

? should appear.
- Click the icon once and choose "Format Disk" from the menu.
- You are asked to insert the Workbench disk again. Do it.
- A window appears letting you to choose some options. Insert the empty disk again.
- Click on Format. Confirm that you want to format the disk and wait until it is finished.
- Now carry the empty disk to your PC and copy the downloaded archives to it.
- You need hdinst.lha, rdbrecov.lha and lha.run.
- While the PC is copying, go back to the Amiga and insert the Workbench disk.
- Select "Execute command" from the menu and enter "newshell" into the command line.
- Enter the following commands into the DOS window:
copy c:copy ram:
copy sys:system/format ram:
cd ram:
- now fetch the disk from the PC and insert it into the Amiga's drive.
- enter
copy pc1:#? ram:
lha.run
- now get another empty floppy and insert it into the drive (you can use the PC disk if you don't have another one)
- enter
format drive df1: name empty2 noicons
- press return twice.
- enter
lha x #?.lha df1:
Now the new disk contains HDInstTools which is a freeware replacement for HDToolbox and RDBrecov which is a command line utility to search partitions on a HDD. HDToolbox has an icon and can be run from Workbench. RDBrecov has to be run from the shell window. In order to read the documentation of RDBRecov enter the following command:
sys:utilities/multiview empty2:rdbrecov.guide
Note that as long as you only edit partitions, your data is safe. Use HDInsttools to create the partitions RDBrecov has found, then reboot to see if the data is back. If not, try again. Keep away from the "DOS format" and "copy disks" buttons !!
Bye,
Thomas