Firstly, as Shohom says, check if you're using the Incognito mode. If the appears next to the tab name, you need to follow the instructions from the official web page, in order to close this mode.
If you aren't in the Incognito mode, go to Start > Control Panel > Uninstall a program, select Google Chrome from the list and click Uninstall. Make sure that the box next to Also delete your browsing data is not check and press Uninstall again:
After that, download the latest version of the browser and install it following the on-screen instructions. This should fix it.