CAUSE
Error 1721 is an Install Shield error code which indicates that the installation process has failed.
SOLUTION
- Disable/Configure any anti-spyware or anti-virus software on your system during the installation process.
- Check to see if any spyware or adware is installed on your system blocking the completion of install process.
- Check to see if you find any unwanted entry in Add/Remove Programs or Internet Explorer - Add-ons section (Tools - Internet Options - Programs - Manage Add-ons). If you found one, remove/disable this entry.