Manually remove SCOM 2012 or SCOM 2007 R2 Agent

I was doing a migration project from System Center - Operations Manager 2007 to System Center - Operations Manager 2012 R2. Some computers had troubles with the upgrade of the agent. I first tried to do a client push deployment. 80 % of the installations succeeded, but I had a couple of computers with failed installations/upgrades. 1. Start the agent installation manually on the failed computer. Run the MOMAgent.msi installer. 2. Click “Next”. Accept the terms and click “I agree”. 3. Notice the “Upgrade” button instead of the “Install” button. 4. Close the setup and check the solution below. Solution: I was able to fix this to remove the product registry key of the SCOM 2007 Agent. You can find it at HKEY_CLASSES_ROOT\Installer\Products\. Search for a key with ProductName “System Center Operations Manager 2007 R2 Agent”. Back-up your registry and remove the key. Try the setup again and notice the “Next” button instead of the “Upgrade” button. The agent push will work now.