Q: reinstallation nouveau disque dur imac 4.1

There is very little you  can't do with Snow Leopard that you can do with Leopard, and the installation discs are cheaper and still available from the Apple Store online.  I would upgrade to 10.6 but not 10.7.

ALso the 4,1 if that is what you have should say Intel, not PowerPC.  If that is th case you should have posted in the Intel forum.

The EFI firmware update would be applied to the hardware in the computer.

The logic board has a chip that stores those details; not on a hard drive.

Changing out the hard disk drive would not alter this fact; so there may be

different reasons for the computer not accepting a system install DVD, etc.

If you happen to have a late model G5 iMac PPC, it could look like the later

Intel-based Macs. You need to correctly identify the computer, since there

were many models built and they have different specifications.

If your computer looks like the newer pizza box models, it would be here:

Identify the model of your iMac - Apple Support

If the computer is like an iMac G4, it would be the model with the chrome

metal arm, and half-orb base, with the newest OS X it could run, 10.5.8.

Those were from about 2003 and are powerPC hardware. What is yours?

And if your computer is an iMac4.1 it would be one of these Intel models:

Both 17-inch and 20-inch iMac4.1 (intel-based) from Early 2006, note software.

Original OS    Mac OS X 10.4.4 (8G1165, 8G1171, 8G1172)

Later OS    Mac OS X 10.4.6 (8I2040)

Maximum OS    Mac OS X 10.6.8

Hardware Test    AHT 3A100, 3A103

• iMac EFI Firmware Update 1.1

Original media would be grey label, specific to the Intel based iMac model; with

part numbers intended only for use in the iMac4.1 (Intel. Not PowerPC G5/G4)

If you have a retail 10.5 OS X Leopard DVD, that should work; start with C key

held down and choose through the setup instructions; use Disk Utility from the

menu to set up (format) the hard drive in HFS+ Journaled... then the installer

can see the drive as ready for the full installation. Exit Disk Utility to complete

the installation. Have you previous experience with new system installation?

This EFI Firmware Update fixes several Boot Camp,

start up, & wake-from-sleep issues on iMac computers.

It was supplied & available back in 2006 in OS X10.4.6.

The computer should be able to boot into the Installer on the OS X DVD so as

to prepare the hard drive for a fully new installation; using its Disk Utility...

A host could be asked to relocate this thread to the Intel-iMac section for best

exposure; however there needs to be more information supplied, even so.

Good luck & happy computing!

Another item to check and also consider replace, is the clock battery (aka 'pram' battery)

that lives on the logic board, as once these no longer hold adequate power, the iMac may

not wish to start up or run properly. Add that part to the list of things to get & install, to test.

Thought to add this, since there's been no activity from you on this or any other thread so far.

If your computer is a G4 iMac with chrome display support arm, and half-orb base; it has a

reset button under the metal bottom plate that may need to be set for power management.

Helps to double-check the identity of the model and supply more information, to be sure.

A G4 iMac ^ model  (like the icon in your user page) is older and not of Intel architecture.

For All iMac model technical information, upgrade info, and repair spec across time, see the links below:

• Apple iMac Technical Specifications - All Models - everymac.com:

http://www.everymac.com/systems/apple/imac/index-imac.html

• iMac Repair Guides - iFixit.com:

https://www.ifixit.com/Device/iMac

So detailed identification is very important if asking a general question on a specific model.

Good luck in any event...!