The installation wizard displays this message when it detects the SmartBear Test Extension for Chrome installed on your computer by earlier versions of TestComplete. That is, this message appears if you are installing TestComplete 15 on the computer, on which you have an earlier version installed.
The Chrome extension that is installed by TestComplete 15 uses the same files (the same file names) as the extension installed by earlier versions. So, the installer needs to overwrite the extension files to make them compatible with version 15.
After the installer overwrites the files and installs the extension, you will be able to record and run web tests with TestComplete 15 in Chrome. As for earlier versions, you will be able to run tests, but recording will not be available. If you need to keep the recording ability for an earlier version of TestComplete, cancel the installation of TestComplete 15 and install it on some other machine.