External Antenna 2

Hi again. I just need to make sure of a few things that were hinted at in
an earlier thread.

My room is lined with aluminium. I cannot get a good signal from my
wireless router even if I have the router in the same room as my computer.
Is this to be expected, or is my card broken?

Can I buy an external antenna (like a desktop one) to run from my wireless
network card to outside the room? Is this likely to work? Which one should
I buy?

If instead I have to buy an access point connected wirelessly to the router,
stick it outside my room and connect it to my computer via a cable, how come
the Belkin access point (for example) seems to cost the same as a Belkin
router, given that the router can function as an access point and do more
besides?

Thanks,
Stuart Dennett