That however is not, AFAIK a .NET issue, and adding it to back up your argument is disingenuous. Exchange checks the OS version and won't install on Win8 or 2012 because of that.
Anyway Exchange 2010 uses .NET 3.5 and you can quite happily install that on 2012 via the usual Add Roles and Features route.
I did genuinely post a link above with the words sys admins and target this specific post;
Digging up it only for information. I had a similar problem but found a solution. The problem is that the WS12 in default use .NET 4.5 and Exchange 2010 need .NET 3.5. Second problem is that you cant install .NET 3.5 on .NET 4.5.
Short scheme what you need to do to fix this: - Remove .NET 4.5 (it remove GUI and PS3) - Via dism install .NET 3 - Install .NET 4 and GUI
And next when you see you have both .NET 3.5 and 4.5, you can normally install exchange 2010.