I found some "Fujitsu recovery tool" on the edonkey network.
Filename is fujitsu-recoverytoolv202a.zip
Included is a .pdf that says "Fujitsu MPG series HDD recovery tool manual".
Condition: "The harddisk is not recognized by the system but the motor is spinning". Harddisk has to be set to master.
The tool consists of two parts (on a boot floppy). It automatically launches some recovery process (I guess it's flashing a new firmware + checks for bad sectors) and then tries to copy all data to another drive.
I tried the tool on a MPG3409AT which was not recognized even by the BIOS anymore. The tool said immediately "one sector recovered", told me to switch the system off (not: reset it) and when it booted again, it tried to run a copy process (which was not possible because there was no other harddisk connected).
After that, the drive is now recognized by the BIOS again
On another drive that was still recognized by the BIOS (but sometimes the motor stops after longer use) the tool immediately tried to start the copy process.
Maybe this helps someone.
Could send the tool by mail (~1,4 MB). Requests to MPG_user@hotmail.com