[G4] Lost 2 out of 4 Partitions

[John Sparks]

Hello List:
Setting up my new to me G4 Dual 1.25 GHz machine.
I installed the 2 Hard Drives from old  G4/400 (blown PS)
As a point of interest they would not boot, after all my attempts
to do so failed, until I repaired Permissions on all drives, erika.
Then I could boot from them etc.
Today I noticed that the"B & D" drives disappeared from the Desktop.
All traces to where not found,however I did find on "About this Mac"
it showed the Capacity, but no available was blank.????

How do I determine #1 If in deed that something removed all my data.
and # 2 What I need to do to have them mount.

I started with CPU's in 92 on OS 7, and only could afford a new 2nd one,
  the G4,a gift of a G4 TI Book, now this G4 Dual, Every system upgrade
and CPU change has been more troublesome,than the prior.
Not enough to drive me to a PC however.

The best John