updating chrome browser

In September 2011, I installed Portable Chrome Browser 14.0.835.163m in a separate folder on a flash drive. Today,(Dec. 27, 2011) I noticed that there is a new version available, Chrome 16.something. So, I downloaded the new install file. But, when I try to run the installation, I get a message stating that Chrome is already running. I have turned off all my browsers and I still get the message. Do I have to uninstall the old version to install the new? What is required to upgrade Chrome?