Sorry it took me so long to chime in, but I had to gather some information via some additional testing of my own machine. I've got the 2.26 GHz MacBook Pro 13", and do mainly use it in OS X, though I do use Boot Camp for Windows 7 RTM. Here are a number of things to consider...
First of all, Boot Camp includes a BIOS compatibility layer for running Windows, since Macs run EFI (Extensible Firmware Interface). With the x64 versions of Vista and 7, this is unnecessary, since both are fully EFI compatible. The BIOS compatibility layer blunts performance in Windows, as well as taking a fair bit of extra power, thus making it run hotter. If you don't want to use OS X anymore, I would highly recommend installing an x64 Windows directly onto the hard drive without Boot Camp. I've tried this myself, and the difference is pronounced: ~5 hours battery life versus ~3Â½ with Boot Camp (just sitting at an idle Windows desktop). I'm a bit pressed for time, so I'll provide more info later if you would like it.
Newer GPU drivers direct from NVidia may improve the video offloading, thus cutting CPU load.
You could also change the processor policy in the power saver scheme to reduce the max % CPU speed. If 1080p still plays fine, then you can drop power consumption this way. Leaving the Balanced policy alone will allow you to switch back to full performance easily when needed.
The fan is controlled in EFI. The only software written to control it are OS X programs. There exist no Windows programs to do it, including the native Windows 7 fan control.
So the only way to slow the fan down is to reduce the power consumption. In OS X, I use CoolBook to undervolt the processor, resulting in a 40% drop in processor TDP at full bore. Unfortunately, the only Windows undervolting programs are ineffective for full control, but CrystalCPUID should be able to do it if you just need it for desktop use. The only thing it can't do is control the SuperLFM mode, which allows it to idle at 800MHz on battery. CPU-Z doesn't read this halved bus speed, so if CPU-Z says the VID is 0.875 V, then it's actually idling at 800MHz, not 1.6 GHz. Again, I can provide more information if you're interested.
Hope this helps!
Desktop: Athlon II X2 250 | MSI 785GT-E63 | Scythe Ninja | 6GB DDR2-800 | 2xWD6400AAKS & HD154UI | HIS HD4670 512MB | Solo | S12-330 | Win7 Pro x64
HTPC: Athlon II X2 245 | GB MA785GM-US2H | AC Alpine64 Pro | 2GB DDR2-800 | WD5000AAJS | NSK4480 | EA-380 | Win7 HP x86