How do I re install Amnesia?

[saiyan]

I tried to do a full conversion mod but I ended up messing up. I haven't done too many of them, I'm still somewhat new to Amnesia. I hit yes to merge folders and then it asked me to replace some files. I thought I was supposed to do that so I hit yes to all. Now when I try to play that full conversion, I get this:

"Amneisa.exe caused an EXCEPTION_ACCESS_VIOLATION in module ntdll.dll at 0023:776A7245, LdrUnlockLoaderLock()+1465byte(s)"

I sent a message to the creator of the mod and he recommended that I re install Amnesia again. I bought the game through the website (amnesiagame.com). I have the license number to my game. Amnesia is my first real PC game, I rarely install anything on my laptop so I don't do this kind of stuff everyday.

My overall question is this, how can I re install Amnesia without paying for it again? Or do I have to pay for it again?

I'm assuming I might have to uninstall the game first then re install it, but once again Amnesia is my first PC game so I've never had to do anything like this, I'm a noob when it comes to that. Thanks for any help/advice, I truly appreciate it.