Thank you for your response. I am working with the 9.0 version. The 8.5 version was uninstalled. I have tried the machine recovery process as you suggested, but the problem persists. After uninstalled the 8.5 (before 9.0 installation) I searched machine registry and realized that many records related QV still remained. Other thing is that the license information is still appearing in the License Enabler File Editor in both Current License Key and Current License Enabler File fields. Is there some script that uninstalls QV completely including registry records and other .dll license files? I will appreciate your help.