MSI: How to check that product is actually installed

I have system that install via internet several MSI products and I have a situation - tester delete folder with product, but not the registry keys and my system see that the product exists via registry and it tries to upgrade it, but开发者_开发技巧 product actually didn't exists.

Is there any MSI function which help me determinate the state of product in silent mode and if user delete files - uninstall the whole product?

if you just need to check whether the product is still registered with Windows Installer - convert your package's product code to packed guid format (e.g. by using script from http://www.dwarfsoft.com/blog/2010/06/22/msi-package-code-fun/) and search for its presence in HKCR\Installer\Products.

To actually remove the product from Windows Installer database - the simplest way is to use MsiZap from http://msdn.microsoft.com/en-us/library/windows/desktop/aa370523(v=vs.85).aspx.