2007 iMac: Boot Camp options

I have a 24" mid-2007 aluminum iMac that's been in storage for a while, and I'd like to bring it back into service, if for no other reason than the nice big screen. It currently has Yosemite 10.10 loaded, and I intend to load 10.11 once I dust it off. However, I'd also like to install Windows on it. Preliminary research seems to indicate that Apple only support Windows 7 32-bit on this particular model. Is this true? The hardware should be capable of running Windows 10, and I've read at least one report of someone getting Windows 8.1 running on this model. (I learned a long time ago that just because Apple doesn't support it, doesn't mean it's not possible.) Where would I get a copy of Windows 7 32-bit? It's no longer in retail channels.

This machine also has an issue with a faulty heat pipe and likes to overheat, so under OS X I've been using a fan control program. Are there similar programs for Windows?