Question : Problem: Is 'normal' ATA hard drive compatible with iMac (Flat Panel)?

I am installing an IDE drive in an iMac (Flat Panel).  The original drive (Seagate Barracuda) is somewhat 'wrapped' in metal shielding (including the PCB).  My replacement drive has exposed PCB.  I'm afraid if I install the new drive something will short out or arc against the metal drive carrier.  

Is this a legit concern.  Must I purchase an Apple IDE hard drive?

Answer : Problem: Is 'normal' ATA hard drive compatible with iMac (Flat Panel)?

No, you don't have to use and Apple IDE drive.

See the following websites which detail replacing drives in iMacs
http://www.macupgrades.co.uk/store/machine.php?name=imac-g5
http://www.dtgeeks.com/index.php/features/tutorialview/imac_g5_hard_drive_replacement/