You can update the application by simply downloading the trial version from the official website, then you can use your serial number to register it for the full version. You need to access the download form. Fill it with your details and an email will be sent to you. That's what I did. After registration, an email will be sent to you.
Download form: http://www.twensoft.com/Image-Expert-Download
I have installed it on Windows 7 Ultimate x64 and it works normally.