I have installed Windows 8.1 Professional x86 on an early 2008 24" iMac (8,1) using Boot Camp Assistant (with the shipped OS X 10.5.4, before upgrading back to 10.9.5). I would have installed Win 8.1 x64 but I couldn't get the install disk to boot up because of EFI version issues on this older iMac. The OS boots up ok but it seems to crash nearly every time I run it, usually when performing some fairly light tasks, such as clicking on a browser link or otherwise. The screen goes black and the computer is unresponsive. I thought initially it might be a display driver issue, rather than an actual system crash, so I had a CD playing the next time, and after the screen went black, I still got sound for a few more seconds but it faded out and stopped, suggesting it definitely was an OS crash on each occasion. Although there is no version of Apple Boot Camp that will install on Win 8.1 x86 (unsupported), I did install the drivers that I downloaded from Apple, and they didn't seem to make any difference to the problem I was experiencing with crashing. I tried to install the latest (correct) version of driver for Win 8.1 for the NVIDIA GeForce 8800 GS 512 MB graphics card but it messed up Windows so badly that the system rolled back to a previous configuration. I have also just yesterday reinstalled Windows 8,1 Pro, but keeping my files and programs, but it hasn't made any difference to the crashing problem. I don't see any reason why it wouldn't work, given that Win 7 x86 is supported by this particular iMac. Do you think it is likely to be a driver support issue? Or an installation issue? I could try wiping the entire partition and reinstalling Win 8.1 Pro again. Any other ideas? I have in the past managed to install Win XP in Boot Camp using the original iMac OS (10.5.4) and it was rock solid stable. I have heard Win 8.1 can be rather unstable but surely not this unstable? Has anyone experienced this type of issue with Win 8.1 on an older iMac? Many thanks!