Any serious risk in installing outside Program Files?

Is there a definitive answer to this question?

There are programs that by default install in a sub-directory on C drive, but outside Program Files (or Program files (x86)).

Is there a risk in doing so or, put another way, is there an advantage in installing under Program Files? I don't see any apparent disadvantage from a risk point of view since I consider that a hacker or malware would try and attack any file(s) no matter where they are located on one's hard disk. Even so, perhaps an attack may focus on the more common areas such as Program Files.

Yes there is a difference and its a pretty big difference. If a program is installed outside of the program folders then it will bypass your UAC Settings. Not sure if most will agree with me on this or not, but an ideal UAC Setting in my opinion is level 2 out of 3(this means one notch from the very top). As long as you know how this program that you are installing works and what it should be doing, then you can make a smart call as to whether its ok to install it outside of the program folders. The main reason I said that its a big difference is because most Virus' are not really so much categorized as a virus its probably a better idea to call it "Programs People Dont Want", so the UAC being at a level 2 or higher is the only way to know for sure if changes are being made to the hard drive without your knowledge. Just make sure that you always pay attention if your computer is prompting you because a program wants to make changes to your pc, if you get a prompt and you do not know the program that you are being prompted for then make sure you say no. If you take those items into consideration then I would say its probably ok to install the program outside of your program folder, and if you are going to do so, I think you might want to consider maybe installing it to your "Documents" folder or your "Appdata" folder. I like the appdata folder because it keeps the program sort of behind the scenes or out of your regular viewing area where as in your my documents, it can start to get messy if you install too many programs there.

Some programs/apps. get installed under the %AppData% folder. I do not like this trend, but they work properly.

@DigitalBil I checked the UAC and it's at the highest level (described in the relevant settings dialog as "Recommended").
@Try3 I checked the access permissions the application has set up for its installed folder and they are the same as those of the Program Files folder.

I'll also try to run this program in a sandbox in order to increase security.