A couple of weeks back I thought I'd have a go writing a Windows Store App. To this requires Windows 8. At the time I was running Windows 7 Home Premium on an early 2009 iMac 21.5 (Core 2 Duo). This had been installed using Boot Camp including install Boot Camp assistant and the drivers supplied by Apple.
To upgrade to Windows 8 I wanted to avoid a re-installation of all my apps. and data etc so I went with an in place upgrade. This all seemed to work properly and soon I was running Windows 8 and could access the Windows Store App templates from Visual Studio. However, soon after Windows 8 kept crashing, well freezing. It got to the point that after every reboot I'd be lucky to get 5 minutes of up time between each freeze.
Given that Apple haven't provided Windows 8 drivers yet this wasn't exactly a surprise. I decided to try and work around this by rebooting to OS X and using VMWare Fusion to access the Boot Camp partition. Whilst rebooting in OS X I managed to corrupt the Windows installation. I use a non-Apple wireless keyboard (as I need the insert, delete, home & end plus the easily accessible cursor keys for VS development) so holding down Alt to select the OS to boot into didn't work. When I realized it was going back into Windows I just turned the machine off. After a couple of times the Windows installation was toast! To get back to the point of trying Fusion I had to do a fresh Windows install. In this case installing a minimal Windows 7 installation: just enough to allow the download of Windows 8. I then installed Windows 8 using the preserve nothing option.
Having now gone through the steps I wanted to avoid I decided to give the new installation a go via direct boot, i.e. no Fusion. That was two weeks ago. Since then I've re-installed all the apps. and my personal data and (fingers crossed) haven't had a single crash. As the freezes were usually happening during some graphical operation e.g. a status bar updating I assumed the fault probably lay with the video drivers. I didn't install Boot Camp assistant and in particular the Windows 7 drivers from OS X disc. Well, I did install one. After a while I noticed I wasn't getting any sound even though all the audio drivers and hardware claimed they were happy. Eventually I installed by the Cirrus Logic driver which made the speakers work. I haven't gone anywhere near the NVIDIA drivers.
So, the whole point of this post is for those who run Windows via Boot Camp on early iMac's that if you want to run Windows 8 then perhaps a fresh install (or maybe uninstall the Boot Camp supplied drivers prior to upgrade) is probably the way to go.