SharePoint sites do not allow admins to sign in

A - OBJECTIVE: to configure settings at a fresh SharePoint server.

B - PROBLEM:

Provided a System Account (domain account at AD) with Site Collection Admin permission, when this admin try logging into the system, SharePoint site keeps prompting for login. It makes the problem looks like : the user enters the wrong password.

C - SOLUTION:

To create or edit an entry at RegEdit.

D - STEPS:

1.     Click Start, click Run, type regedit, and then click OK.
2.     In Registry Editor, locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
3.     Right-click Lsa, point to New, and then click DWORD Value. Type DisableLoopbackCheck, and then press ENTER.
4.     Right-click DisableLoopbackCheck, and then click Modify. In the Value data box, type 1, and then click OK

Note: In 64bit machines, kindly select DWORD(32-bit) value