Jay feather already told you all you need to know.
If it worked before, it must be something you've done or the game has done. And all I believe it has was just changing the rendering subsystem.
If it was the computer it would be hard for anyone to track back what it could've been.
As jay already suggested.
Uninstall the game
Remove the FH folder in C:\FeralHeart
Install the game again.
That would solve anything if it was the game. And if you still have issues it must be the computer itself unless it just isn't the rendering mode.
If it is the rendering mode, or that you need to install drivers. It ALL should be explained to you in the link jay sent you. But that means you actually read it through.
To me, by just reading the replies, it seems like you're a tad bit lost. I'd suggest you to read the help thread through once more since errors doesn't fix themselves.
If you're unable to still sort it, after following all the advices. Yes, then it's most likely a permanent change to your computer we can't be aware of.
Read the whole post here
http://feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=10423.msg144821#msg144821