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
https://support.microsoft.com/?kbid=909967

Windows Installer Clean-Up Tool
https://download.microsoft.com/download/E/9/D/E9D80355-7AB4-45B8-80E8-983A48D5E1BD/msicuu2.exe

Uninstall SQL Server Management Studio
https://support.microsoft.com/default.aspx?scid=kb;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)

https://support.microsoft.com/default.aspx?scid=kb;EN-US;922670

Uninstall SQL Server Express
https://msdn2.microsoft.com/en-us/library/ms143505.aspx

Fatal error during installation
https://support.microsoft.com/?kbid=919945

Uninstall Applications NOT in Install/Remove Programs List
https://blogs.msdn.com/astebner/archive/2005/10/30/487096.aspx