As I see, the applicationpool for my DNN (it's a separate applicationpool, not "DefaultAppPool") is running as ".net 2.0".

The dropdownlist in its properties allows 2.0 or 4.0, but there is no 3.5 option (WHY?). During my module-shopping-tour I found some modules that say they require .net 4.0

How do I find out if my DNN is running as 2.0, 3.5, or 4.0? How do I change it to running as 4.0 (is it simply changing that dropdownlist in the properties of the applicationpool to 4.0 and restart IIS?) and is this even recommended or could this bring some new problems and disadvantages?

Thank you, Bill. Yes, that helped a lot. So I found out my DNN is currently running on 3.5. I am not using a DNN hoster, but have my own VPS (virtual private server) my my own Win2008R2 Standard (64-bit, english) OS running on it. So I am the one with Administrator access. And the .net 4.0 Framework runtime is installed. (It's named "client profile", I think).

Next step I'm considering is to change the applicationpool's property from "2.0" to "4.0" and hoping my DNN will then actually run as 4.0 and therefore will be compatible with those 3rd party modules that explicitly say they need .net 4.0

Can I do that or will it destroy my DNN and/or the compatibility to the (now perfectly working) DNN modules that are built for .net 3.5?