I have the same problem. I even went back and reinstalled all the old versions... what a mess.. still no positive results.
ADE requires Microsoft .Net 3.5 when installing version 1.8 or higher. I'm using windows 8 and have successfully gotten 188.8.131.521 to run. You'll have to pull it off a download site like windows9.com. I assume 2.0 will be updated soon enough to use .Net 4.0.
Windows Update will not install .NET 3.5 for you.
Use Control Panel -> Programs -> "Turn Windows features on or off". You should see .NET 3.5 as the first thing in that list. Select it and click OK. It will install .NET 3.5.
You should be able to install ADE 2 after that.