http://www.smattie.com/2012/03/16/fixed-an-issue-installing-sql-server-2008r2/
see that link and follow all the steps
see that link and follow all the steps
FIXED AN ISSUE *INSTALLING* SQL SERVER 2008R2
As you will remember, I had an issue trying to *remove* SQL Server 2008r2 as noted here. What I failed to tell you was what my REAL issue was… I could not successfully install SQL Server 2008r2 and I kept getting this error:
So I used my tip again to remove the new installation that I attempted last night, which works great, but it still prevented me from installing it. Then I decided to look at the registry and I was surprised… my switch that I corrected last time was set back to zero!! (As seen below)
I made the change back to 1 to prevent switch back and tried the install again. (HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\AppCompat\sbEnable = 1)
It failed again, but this time the registry stayed the same, so I had to remove it and then I went looking into the computer policy to see what might be causing the issue. First I opened it by typing gpedit.msc:
Then I went looking at Computer Configuration, Administrative Templates, Windows Components and Application Compatibility
SO I went through each one and re-read this article to understand the SwitchBack Compatibility engine better. Simply put, switchback is a mechanism that provides generic compatibility mitigations to older applications by providing older behavior to old applications and new behavior to new applications. It should also be noted that switchback is on by default. I turned it off, as seen below:
Behold it worked and just in time for SQL Saturday in Vancouver, BC in Canada. 
