Not in the least bit true. My wife is a prolific reader (a novel every couple of days since she was a child) and her spelling is awful. She has particular difficulty with double letters and apostrophes.
On Mac OS X and Linux, it doesn't take an administrator's password to install software for personal use. On Mac OS X you can drag and drop wherever you want it; on Linux you can build it yourself or convince your package manager to install it into ~ instead of/usr.
If you want the software to be available to more than one user, *then* you need an administrator's password.
Is there a reason this doesn't work on Windows Vista?