CCleaner on 64 bit system

I believe I am right in saying that CCleaner is compatable with a Windows 7 Home Premium 64 bit system. But I have discovered that there are two sets of Program Files in windows 7 64 bit systems, one for 64 bit and one for 32 bit systems.

Does anyone know in which set of program files should I install CCleaner, or does it not matter.

Basically, it doesn't matter if you install it on any of the Program Files folder. Perhaps for the ease of determining 32-bit/64-bit software, you install it on the appropriate folder.