The Portable version of the Smart Client is not registered with the Windows Installer Framwork and can therefore not be uninstalled from Programs and Features (This is the tradeoff for being able to install without Administrative permissions in Windows).

The Portable version of the Smart Client can be 'uninstalled' by simply deleting the directory where the Smart Client was installed to. By default this is a subdirectory of the LocalApplicationData of the windows user who installed the Portable Smart Client e.g. C:\Users\<username>\AppData\Local\redbex\Smart Client\Portableß1.3.14146.14188\.