The HDD's are standard drives. 40GB I think.
Even if the boot sector (master boot record) is damaged, most of the time the rest of the files will still be ok. You'll probably need to get another hard drive to copy the original onto. Just make sure you don't to any drive copying or modifications using a system that runs Windows XP - it will mess up the file system on the drives. Best thing to do is to do it all on the machine itself.
Get yourself an old Dos boot disk and boot the machine up from the floppy. Then you can do some more thorough investigating. To copy the drive you'll need to get a copy of Norton Ghost that can run under dos and from a floppy disk.
This technical bulletin from Siemens will give you some more insight on backing up the HD.
http://members.shaw.ca/jasoncmckenzie/A21_049C.pdf
good luck