It's fairly common knowledge by now that Windows 8 breaks some customized Kirikiri Engine games (you'll know you have one if your game uses .xp3 files) that uses legacy calls to Windows libraries pretty badly. It will say : Authentication failed - Unrecognized Win32 Module. And it will not start. No matter what. If you're in luck, the company would have a patch for this released. If they'd folded or gone quiet already, well, there's not much hope of that.
I haven't checked if there are Kirikiri Engine BL games that don't work in Windows 8, but if you run into one and there's no patch----use this : http://resemblances.click3.org/?p=1406
Download Win8WOH.zip, copy version.dll into your game folder, you're set. I've tried it on some otome and eroge that didn't work before, it does what it's supposed to do. Though it's not guaranteed to help *everything*.
I don't know if this info will ever become necessary, but I'm putting this here, just in case.
(Please move this thread if it belongs to the wrong section!)