Okay. Both are v2.4.

If you are using Vista, Win7 or Win8, make sure to install them using the "Run as administrator" option.
To do this, right click on the installation files (csp721_2400.exe and csp723_2400.exe) and from the list that appears, select "Run as administrator".

[edit]You should download and install the latest version of FSUIPC.

Read this: FSUIPC will need replacing on all user systems!

I'm not sure if te 727 Base Pack installs an earlier version of FSUIPC, but it would be a good idea to check to see which version is installed once you've finished installing the Base Pack.[/edit]