SQL Server Setup has encountered error

Hello,
I upgraded my server to SQL Waiter 2011 Denali. Then, my friend asked me to install SQL server 2007 R2.
So, I uninstalled SQL waiter. Then I received an error message which myself and my friend failed to resolve.
Kindly help me in fixing the below issue.
Thank you for all supports.

SQL Server Setup has encountered the following error:
Method not found: ‘Boolean Microsoft.SqlServer.configuration.MSExtension/metadata.get_1xSlpstreamOrPath()’..
