Root Cause: Lot many root causes for this.
Some of the root causes..
IIS
-Application Pool might be stopped. Start the app pool, it will solve the problem.
-Open Application Pool "SharePoint Central Administration" properties. enable32BitAppOnWin64 should be false.
-Application pool password might be wrong. Go Identity, update Password.
-SharePoint 2010 runs on .NET framework 3.5 not 4.0. So in IIS you have to set .NET Framework 2.0
config
-Open applicationHost.config file, search for "SharePoint14Module" modified to below
<add name="SharePoint14Module" image="C:\Program Files\Common Files\Microsoft
Shared\Web Server Extensions\14\isapi\owssvr.dll" preCondition=
"appPoolName=SharePoint Central Administration v4,bitness64" />
Some of the root causes..
IIS
-Application Pool might be stopped. Start the app pool, it will solve the problem.
-Open Application Pool "SharePoint Central Administration" properties. enable32BitAppOnWin64 should be false.
-Application pool password might be wrong. Go Identity, update Password.
-SharePoint 2010 runs on .NET framework 3.5 not 4.0. So in IIS you have to set .NET Framework 2.0
config
-Open applicationHost.config file, search for "SharePoint14Module" modified to below
<add name="SharePoint14Module" image="C:\Program Files\Common Files\Microsoft
Shared\Web Server Extensions\14\isapi\owssvr.dll" preCondition=
"appPoolName=SharePoint Central Administration v4,bitness64" />
