Is .NET 4.8.1 the same as 4.8.09037?

Hi @John Mcgregor [Contractor] and thanks for posting your question.

4.8.09037 is the internal build number shown by the registry, while 4.8.1 is the public product name. They are not two separate .NET Framework products.

To verify the installed release correctly, open:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full

Then check the Release DWORD rather than relying only on the Version string:

• 533320 or 533325: .NET Framework 4.8.1
• Any higher value: .NET Framework 4.8.1 or a later applicable release

You can retrieve it with PowerShell:

Get-ItemPropertyValue `
  'HKLM:\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full' `
  -Name Release

Therefore, if you see Version = 4.8.09037 together with one of the release values above, your computer has .NET Framework 4.8.1 installed. Microsoft recommends using the Release value as the authoritative way to determine the installed .NET Framework version.

If this instruction is applicable to your situation, I would greatly appreciate it if you could follow the instruction here so others experiencing similar behavior can benefit from it as well.  

You can refer to Microsoft's guidance on how to determine the installed version of the .Net Framework at -

How to: Determine which .NET Framework versions are installed