Well, you don’t exactly need new or another copy of GTA, you just need to delete dinput8.dll from your main GTA directory and thats all. If you want to play LSPDFR again after, you just add dinput8.dll back to your directory. I personally have dinput8.dll on my desktop and when I want to play LSPDFR, I just drag and drop it to my GTA directory.
dinput8.dll is the file for ASI Loader in OpenIV