Well, if you have ever tried to manually uninstall SQL Server 2005 or onwards then you would definitely know the pain. There are so many components in it and we definitely don’t know the right sequence of deleting them. So unless a miracle happen, you will be getting an error of something like ‘X depends on Y, so dude you can’t delete it’ or worst ‘X did depend on Y and now that you have deleted the Y , so just go and pull your hairs out.’
Mercifully, Microsoft has this cleaning utility which works like a charm and is unbelievably fast. You can delete everything blindly. you can check it here
http://support.microsoft.com/default.aspx?scid=kb;en-us;290301