Dear sir,
Please follow below steps to verify .NET installation:
1. Open "Command Prompt"
2. Copy this command and hit enter :
reg query "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP"
3. You will get something like below image:
Verify you have v3.5 installed. You need minimum v3.5 installed in system to run ERA Explorer. If not available, follow below steps:
1. Go to Control Panel
2. Open Programs & Features
3. Open "Turn Windows Features On & Off" in left bar on top section
4. Tick for Microsoft .NET Framework 3.5.1 and Click Ok
5. Restart your machine
If problem persists, Check for administrator privileges and scan your computer for viruses.
I Suggest to install Dot Net 4.0 Extended which is supportable for ERA As well as MS-CIT Exams
https://www.microsoft.com/en-in/download/details.aspx?id=17718