How to un install SQL Server 2005

You can use these docs for uninstalling your 2005 sql instance based on your requirement.

Uninstalling an instance of SQL Server 2005 manually

Windows Installer Clean-Up Tool

Uninstall SQL Server Management Studio;EN-US;909953

Using the Add or Remove Programs item in Control Panel to add
or remove components for stand-alone installations and clustered
installations of SQL Server 2005 (KB: 922670);EN-US;922670

Uninstall SQL Server Express

Fatal error during installation

Uninstall Applications NOT in Install/Remove Programs List