Install / uninstall impossible

Although my hardware (8 Windows Pro) meet (Tablet PC) and the operating system all the requirements of the software, an installation with functional result is impossible. The uninstallation ends without useful result with reproducible crash the installer. The calculator is to enable only through the Restore a backup created with another system or by laborious manual rework the registry back to an acceptable condition.

So just "banana ware" behaves (goods matures at the customer)! I do not rule out that there are systems that manage a fully functional installation, but can not even uninstall the product clean, is a disgrace.

What confidence can we have in such circumstances in a "Backup" and whose recoverability?