I don't use Steam, so this may or may not help. That said, before reinstalling, after using the uninstall option, check the location where Steam installs CIV to be sure that all traces are gone. Also, check the registry to be sure that it does not still show CIV installed. If there are empty folders in the CIV install area or if the registry still shows it installed, then the installation program will skip parts of the install, "thinking" that they are already there, even though only empty folders or registry entries, without actual files, remain. Similarly, if you manually uninstalled CIV by deleting files and folders, the registry will still show it installed, messing up the new installation.
To look at the registry use the program "regedit". It is part of the Windows 7 OS but it is hidden. To access it type "regedit" in the search box of the start menu. Be careful using it! Don't edit anything that you don't understand. You can trash your Windows 7 install, if you do. Just look around for CIV. When you find where other programs are installed, look for CIV. If it is not there, or is marked as deleted then you are okay. I can't coach you further on this, as I have not had to use regedit to change anything.
