Need help... Cannot see one of my internal HD's

[FlipSwitch 0]

I recently purchased a new Mac tower... which is running lion

 

Hardware Overview:

 

Model Name: Mac Pro

Model Identifier: MacPro5,1

Processor Name: Quad-Core Intel Xeon

Processor Speed: 2.4 GHz

Number Of Processors: 2

Total Number Of Cores: 8

 

I took 2 of my old hard drives from my last computer and installed them into the new computer... they all booted up fine... after I restarted a relized only 2 HDs were showing up... but When I do an install for an app and change the location for the install I can see the 3 HDs... how do i access the one not showing?... I think both of them are named Macintosh HD and the other is named Macintosh HD2... so one that i cannot see has the same name... when i do a search i only see one... sorry if this message is jumbled or confusing... just exaushted... anyway still getting use to lion and the desktop not showing the hard drives and all these other quirky things... maybe its a setting im missing? maybe its because they are bothed named the same thing?... any help is greatly appreciated and i can clarify any questions...

[superegophobia 0]

I'd backup before you do anything. Do all three drives show up in Disk Utility? Can you rename it from there and repair permissions? Sometimes using Disk Warrior has helped with random drive issues like that.