SQL 2008 R2 SP2 Install problem

Hi all~~
There is problem when I am trying to install SQL 2008 R2 SP2 problem
the existing is

Microsoft SQL Server 2008 R2 (SP1) - 10.50.2500.0 (Intel X86)
 Jun 17 2011 00:57:23
 Copyright (c) Microsoft Corporation
 Standard Edition on Windows NT 6.0 <X86> (Build 6002: Service Pack 2) (Hypervisor)

and it shows that when during selecting the instance. it was not allow me to choose that instance......