Checking your .NET Version can sometimes be confusing and frustrating. You can have something listed in Programs and Features or Server Features, but this may not reflect the latest version of .NET currently installed. The best way to check which version of .NET you have installed is via the Registry.
There are more details in the KB article about older versions of .NET, but this should at least pont you in the right direction if your K2 Server is not starting.
If you dont have the necessary rights to view the registry there are 2 other ways:
1. Using Windows Explorer:
All Microsoft .NET Framework versions are installed in following directory:
So just type the above mentioned path in RUN dialog box or in Windows Explorer addressbar and press Enter. Here in this folder, you can find out which versions are installed, by checking the folder names.
2. Using Command Prompt:
Open Command Prompt from Start Menu and execute any of following commands:
wmic /namespace:\rootcimv2 path win32_product where "name like '%%.NET%%'" get version
dir %windir%Microsoft.NETFramework /AD