I had this problem constantly with every game on my Vista, and still have this problem with a lot of my games on Windows 8... If you haven't gotten FH to work yet, and you've tried what the others have suggested, then you could be having a DEP problem, aka Data Execution Prevention. To put it simply, DEP hates you, your games, and your computer programs overall. It will go out of its way to ensure you cannot play games and programs even though there's nothing wrong with them. It will also strike randomly on games and programs that worked just fine the day before. It's a broken feature that should have been done away with long ago.
...but anyways, what you want to do is open your Control Panel, go to System and Security, and then go to System. Then go to Advanced System Settings, then under the Performance tab (or Performance section, whatever, you might have to search the tabs for it, but it should be the only thing labeled Performance in the dialog box) click on Settings (or Performance Settings, not sure what it will be called in Windows 7).
After that another dialog box will pop up, and one of its tabs should say Data Execution Prevention. Click on it, and then make sure "Turn on DEP for all programs and services except those I select" is selected. Then go down and click "Add..." This will allow you to add Feral Heart as an exception to the dreaded DEP. Find FeralHeart.exe from the Open dialog box (It will be in your Feral Heart folder, obviously, so just find that, and it will be the only thing that shows up in the folder besides other empty folders and the uninstall application). After you add Feral Heart to the list, click "Ok" on the bottom of the dialog box to save your new setting.
If this doesn't end up working, then you will have harmed/changed absolutely nothing by adding Feral Heart to you DEP exception list. It will not effect gameplay, performance, or absolutely anything. But if you wish to remove Feral Heart from the DEP list just make sure that the box next to Feral Heart is the only box checked, them simply click Remove.
(If you can't find any of the tabs I talked about, or if things are labeled a lot differently, try here instead:
http://www.online-tech-tips.com/windows-xp/disable-turn-off-dep-windows/)