According the SMC Fan Control my ODD Optical Drive fan is running at 0RPM's and I an not able to get it going via software....bummer. At least now I know.
I had absolutly no problems running Bootcamp Win7 install on my mid 2010 imac 27", so the win7 black screen certainly doesn't effect everyone.
My imac was also ROASTING hot when I ran windows 7, so then I used the macfan utility to increase the fan speeds manually.
I am sorry to hear your ODD fan has failed, or perhaps isn't connected, but you did a great bit of troubleshooting, well done!
In general terms I wonder if in Windows 7 there is no "Software" running to cool the imac, and the fans kick in too late, once the system is already cooking. I find MacOSx runs cooler, and think there maybe some code that is more reactive.
I now just set the fans up a notch for normal Windows 7 use (And set them, way higher for gaming).
I also replaced the Bootcamp GPU driver with the latest ATI mobility driver, which again might mess with the fan control, so this is another reason I like to use the macfan to keep an eye on things.
I really don't like running computers hot, so MacFan is a great tool in that respect.