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You can install Windows 7 on Boot Camp on your computer without any problem.
The last link says that only Late 2009 and newer iMacs are compatible with the 64-bit Windows 7. I mean, you can install a 64-bit Windows 7 because you have a 64-bit processor, but 64-bit Boot Camp drivers aren't available for your Mac, so Windows won't work properly.
In conclusion, if you want to use Windows 7 on Boot Camp, install the 32-bit Windows 7 version
mende1, thanks for the response.
OK, so I'll go for the 32-bit version.
I was a little confused initially because the only reference to 32-bit in http://support.apple.com/kb/HT1846 is that iMacs later than mid-2011 can use either 32- or 64-bit i.e. the newer machines can use both. Perhaps the post would benefit by clarifying the 32-bit only requirements for older machines like mine.