Chrome can 'run in the background', so you might have uninstalled it (or at least thought that you'd uninstalled it) while it was still running.
Open your Task Manger (via right-clicking on the Task Bar at the foot of your screen) and select he Processes tab. If 'chrome.exe' is listed, it's still running. If so, click on it to highlight it and then select 'End process'. Then try uninstalling Chrome again, before restarting your computer and reinstalling.
Alternatively, remember that 'a certain extension' also works with Firefox ;-)