Sounds like you just have a straightforward connector adapter, not a component to VGA adapter, and that won't work. You need a BIOS that outputs VGA instead of component, and you need either a monitor that supports sync on green, or an external sync separator (or a cable with an inbuilt sync separator). This post
has loads of detail, and this
is a ready-made cable with a sync separator you could use.
Alternatively you could buy a genuine component to VGA adapter - an active one that requires power.