Installation of Windows 7 Professional SP1 failed

Hello Sheila, thanks for your answer...

Actually it doesn't solve my issue, cause I have any upgrades on it.

Now, my iMac doesn't recognize ANY Windows DVD's (the one burned with an ISO downloaded from microsoft too) as bootable, so installation never starts after reboot.

I tried to install by USB pendrive, using the ISO I mentioned before: well, I selected all three options in Bootcamp Assistant, choosing the right ISO file, but it told me it's "Impossibe to create the bootable USB unit", cause "an error occurred during disk initialization"; trying a second time, I bypass this message, but I get "Failed to copy windows support files". It's strange, cause I alredy used the same pendrive to install another copy of Windows before: I removed it cause I've got a license for "Pro" version (it was "Ultimate"), but I can't figure out why it doesn't work this time.

I didn't make any changes to my iMac, but I ask you: could any app or option create conflict with bootcamp?

Please, help me

PS

Is it possible to manually do things that Bootcamp assistant does? It may solve the problem I guess... I've found some tutorials, but unetbootin didn't solve the problem, and all others want me to use a windows pc to create bootable memory stick...

I tried, but didn't work. I tried all these steps: installation DVD I bought, ISO manually burned into a DVD, and ISO directly... I also tried this: manually created a MS-DOS FAT partition named BOOTCAMP, initialized pendrive (FAT too), used Unetbootin to make it bootable by downloaded ISO, put in it windows support files. It seemed to work, but after reboot, pendrive were recognized as non-bootable, like the 2 dvd's...

I've got the ISO exactly where your link points to, I used a 2.0 usb key for windows support files (it worked fine a few weeks ago), disconnected ALL others usb cables and tried again, following strictly the instructions... No way, it dosen't work. Notice that it stops at first step (formatting usb unit), so it doesn't seem to be an iso problem. Also notice that I tried an OEM installation dvd too, not only the burned iso, but my iMac doesn't recognize them as bootable.

Ah well, I burned that iso with Titanium toast at 3x (the slowest speed allowed).

I already tried this, but I'm going to do it again.

Strange thing: I'm on the screen that ask me to choose the dimension of the Windows partition. When I click "Install" button, this screen appears to me:

Boot Camp has to update the USB drive before installing Windows 7.

The USB drive connected to your Mac has a boot volume. In order to install Windows 7 from DVD, Boot Camp Assistant should disable this function. The unit will not remove any information. Do you want to continue?

I will wait for your answer before going on...

No way, it didn't work.

After reboot my iMac didn't recognize both dvd's as bootable... First time it said something like "No bootable device, press any key to reboot"; second time "CDBOOT: Couldn't find BOOTMGR - No Bootable device -- Insert boot disk and press any key", but in both cases nothing happened pressing keys.

Now I have a BOOTCAMP partition and no clue on what to do to install Windows... What's wrong?

Nothing else, just dvd reader and usb key...

It's atock iMac, on which I had put my old MacBook... I think I made no changes, but... what changes could affect bca?

I'm afraid it's not that the issue... I have a late 2012 iMac 27", without superdrive... I also tried an installation ONLY from USB flash drive (16 GB, USB 2.0), getting error at USB initialization... I'll try these steps. Just deleted windows partition, confirmed that I can see just one partition.

Now I'm going to reset PRAM, and to do permissions repairs...

Then I'll try again windows installation and will report to you.

Thanks so far...