Q: install windows 7 imac  Yosemite

I somehow missed this

I removed the Freeagent drive.

as long as diskutil list shows only disk0, you can try Bootcamp Assistant again. If you have any hubs, I suggest you remove those as well.

Does Bootcamp Assistant start up?

Can you post a screen shot of the screen after the first Continue?

If you modify Bootcamp info.plist to get this option, it creates more problems then it solves. On Macs with built-in Optical drives, it is invalid.

Can you roll back to the original info.plist? Does your internal Optical drive function properly? Do you have Windows installer physical media?

Was info.plist modified using a text editor and a code sign command? Did you make a backup of the file, before it was modified?

If you do not have a backup, check the second box "Download software" and verify that the third checkbox can be checked.

Yes, put this back in the directory. codesign Bootcamp again, and then check both boxes in BCA. You will need a USB2 for BC drivers only, and the Windows DVD in the built-in Optical drive. There is no other way to install Windows on your iMac using BCA.

1. Quit BCA.

2. Copy /Applications/Utilities/Boot\ Camp\ Assistant.app/Contents/Info.plist to a safe location.

3. Copy Info.plist.bak to /Applications/Utilities/Boot\ Camp\ Assistant.app/Contents/.

4. Run the following command from Terminal...

sudo codesign --deep -fs - /Applications/Utilities/Boot\ Camp\ Assistant.app

5. Insert Windows DVD. Insert a blank USB2 flash drive 1+ GB.

6. Start BCA. Ensure you have only two checkboxes. Check both and continue.

7. You should see a partitioning menu.