And technically you should just use the 'ProgramFiles' environment variable, since the folder might be called something else if your install is in another language.

And Windows allows side-by-side installs of 64- and 32-bit versions of the same software; so installers should be aware of 'C:\Program Files (x86)' and 'C:\Program Files'; the first is for 32-bit programs on 64-bit machines.

This is just wrong. See

http://news.ycombinator.com/item?id=5176817