post the exact error message if none of the above works.
should now have a different install error -if the original error message was a consequence of installer being blocked.
NB you should not have to install it outside of program files (x86) - that is where programs are supposed to be installed to .
my install is there, in a folder called calibre2 ( dunno why "2" is appended )
also try right click - run as administrator.
I had zero problems installing on 64 bit windows 7 but I have UAC off. do you have UAC enabled ( default setting = enabled) ?