Tiz a bit dodgy Mr Dakar,tried it once under similar circumstances,both disks with win 98 installed one had gone Tango Uniform,installed the knackered one as a slave,entered into dos and typed C: format D:it really porked it, I think it tried to format its own self ie the C: drive or format the D: as a floppy,moment of panic before I yanked the power chord.
Most of the time I have been able to recover duff Hard disks long enough to recover stuff off em I wanted,even took the lid off one once and wiggled the read arms about,it worked fine as a slave and it lived long enough for me to recover my music files an such for about twenty minutes before giving up the ghost.
I usually keep a new hard disk with a clean install of operating system and drivers on me book shelf,if I a hint of trouble from the master in the spare goes and I'm back in business in five minutes.
This is the Draper home made Super Puter from a few years ago, you can see how it was so easy to swap hard disks over.
