The things to check
Firstly go into bios, make sure all 4 drives are set to auto-detect
When computer boots up, it will show what drives are detected, problem
is that it disappears before you can read it.
IDE devices (hard drives and cdroms) usually don't need special drivers,
they will just show up in My Computer.
make sure all cables are inserted properly.
make sure no conflicts with master and slave settings
If a drive refuses to show, put it in another computer and see if it appears
there. If not, it's probably had it.
Tell us what you find.
**
To get into the bios, you press a special key when computer is first turned on.
It's different for various brands. Compaq usually F10, Dell usually F2, other may
be DELETE key. Once you're there look at standard settings (normally first
thing in the list), this is where you set the time and set what floppy and hard
drives.