New Post: How to detect that a client has already an old version of the program to update

MSI ProductCode are specific to version of the application. This mean that there is a MSI ProductCode for KeePass 2.25 and another ProductCode for 2.26.

You need to get the MSI ProductCode for KeePass 2.26.
if the file is a MSI :

• Open WPP
• Go to Tools -> MsiReader
• Load the MSI file
• Open the Dropdown list and select 'Property'
• Search for 'ProductCode'
  

If the file is .EXE :

- Install manually on a computer
- Open Regedit
- Browse to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall
- Search for 'KeePass' and then look at the 'UninstallString' value