Okay, I tried downloading the game through both my browser and the GOG downloader, and both times the installation took hours and when I tried to launch the game I got this message:

"Unable to Execute file.

Create process failed: code 740.
The required operation requires elevation."

Can anyone help with this? If it helps, I'm using a laptop with Windows Vista.

I googled and found the answer. All I had to do was uncheck run as administrator, and it's working fine now.